US3260228A

US3260228A - Ceiling constructions for furnaces

Info

Publication number: US3260228A
Application number: US456079A
Authority: US
Inventors: Lingl Hans
Original assignee: Individual
Current assignee: Individual
Priority date: 1962-11-23
Filing date: 1965-05-17
Publication date: 1966-07-12
Anticipated expiration: 1983-07-12
Also published as: FR1371146A; DE1209038B; GB1023045A; CH416430A

Description

July 12, 1966 H. LINGL 3,260,228

CEILlNG CONSTRUCTIONS FOR FURNACES Filed May 17, 1965 2 Sheets-Sheet l INVENTOR #4444 1mm zszzdzezzazbz A ATTORNEYS.

July 12, 1966 H. LlNGL 3,260,228

CEILING CONSTRUCTIONS FOR FURNACES Filed May 17, 1965 2 Sheets-Sheet 2 INVENTOR HAM Z/A/GL United States Patent 3,260,228 CEILING CONSTRUCTIONS FOR FURNACES Hans Ling], Finningerstrasse 70, Neu-Ulm (Danube), Germany Filed May 17, 1965, Ser. No. 456,079 Claims priority, application Germany, Nov. 23, 1962, L 43,514 5 Claims. (Cl. 110-99) This is a continuation-in-part of application, Ser. No. 319,239, filed October 28, 1963, now abandoned.

This invention relates to ceiling constructions for tunnel kilns intended more particularly for firing ceramic products, and it relates especially to ceiling constructions of the fiat suspended type which, owing to their particular construction, can be made gas-tight and are also suitable for kilns operated at high temperatures on the order of 1000 to 1500 C.

Tunnel kilns with flat suspended ceilings are known in the art. However, a difiiculty inherent in prior ceilings of this type is that they are not gas-tight when substantial differences in pressure are involved. Failure of the ceiling of the kiln to be gas-tight results in an unsatisfactory firing process due to cold air entering the firing space. As a result, excessive cooling of the products being fired and uneven temperatures at different locations within the kiln adversely affect the quality of the firing process.

Flat suspended ceilings have been provided in which special bricks are used, each brick being held in position by means of a screw and a pin, with the pin in serted through a hole in the screw and through corresponding recesses in the brick. However, ceilings made in this manner hold-up only at a relatively 'low temperature. This is due to the fact that the suspension pin carried in a recess in the brick is fully enclosed therein, so that it receives no cooling whatsoever from the outside. Thus, the suspension pin is heated to the full ternperature of the kiln. However, at the temperatures contemplated, the strength of these pins is considerably reduoed so that the weight of the ceiling deforms and possibly even destroys the pins. Deformation of the suspension pins of course causes the ceiling to sag and leak, and if the pins break, the ceiling will collapse.

Another known method of constructing suspended ceilings is to string abutting ceiling bricks onto I-beams which in turn rest on the side walls of the furnace. However, the disadvantage of this construction is that the kiln must be shut-down whenever a ceiling brick becomes defective, because any repair requires that the entire beam be dismantled. Another disadvantage of this construction is that the supporting beam is connected directly to the brick and therefore becomes easily overheated.

An object of the present invention is to provide ceiling constructions for tunnel kilns which avoid the disadvantages inherent -in prior structures of this type. Another object of the invention is to construct tunnel kilns of substantially greater length and width. It is well recognized that the size of a tunnel kiln is limited by the ability of its ceiling structure to Withstand the destructive effects of expansion at elevated temperatures, of the temperature differential between the inside and outside surfaces of the fire brick, of high temperatures on the metal members which support it, as well as of other factors which may be encountered. For example, the length of the furnace has been limited by the amount which its roof can expand at a given elevated temperature without being damaged. Thus, it will be appreciated that if the fire-brick ceiling expands 1% when the furnace is brought up to a temperature of 1000". C., the total longitudinal expansion of the ceiling in a furnace 20 meters long will be only 20 cm. The ceiling may be able to withstand that amount of expansion without damage. However, for a furnace meters long, other conditions being the same, the total expansion lengthwise of the ceiling will be one meter. Prior ceiling structures have not been able to satisfactorily withstand that much total elongation, and even if they did not fail upon initial heating they would be destroyed upon contraction if the furnace is permitted to cool.

Prior tunnel kilns have, therefore, been incapable of withstanding alternate heating and cooling with consequent expansion and contraction, even though they may be able to operate for relatively long periods of continuous operation after being initially brought up to working temperature. However, tunnel kilns incorporating a roof structure in accordance with the present invention may be built several times longer than it has been possible to construct such a furnace heretofore. Moreover, ceiling structures of the invention will withstand alternate heating and cooling many times without ill effect. In addition, not only is it possible to make the furnace much longer by using the ceiling construction of the present invention, but also the width of the furnace may be increased substantially over that previously possible in tunnel kilns.

According to the invention, the ceiling of the furnace comprises a plurality of so-called abutment bricks extending transversely of the furnace and spaced from each other longitudinally of the furnace, each of said abutment bricks being hung by its upper end from a superimposed outer roof structure of the furnace and disposed in sideby-side relation with each other within each row. Between the rows of abutment bricks are carried rows of so-called suspended bricks, which overlap stepped portions of the abutment bricks at both sides, so that their entire Weight is supported by the abutment bricks. The overlapping surfaces of said bricks are horizontally disposed and in sealing engagement with each other in order to prevent leak-age of air or gas through the joints formed thereby.

The abutment and suspended bricks are also disposed relative to each other between rows such that they can expand and contract without shoving each other bodily lengthwise of the furnace. This is accomplished by spacing the vertical edges of the bricks from adjacent parts of the bricks on either side of them longitudinally of the furnace. Thus, due to the overlapping sealing surfaces of the brick, which surfaces can move relative to each other horizontally without impairing the seal between them, and due to the gaps provided between adjacent bricks at their edges, each brick is free to expand longitudinally of the furnace, thereby preventing the destructive additive effect of the expansion of many bricks over a long distance. Since the width of a tunnel kiln is many times less than its length, both the abutment and suspended bricks can be rigidly pressed together transversely of the furnace in order to force the mutually engaging sides facing transversely of the furnace into gastight engagement with each other. Any expansion in this direction is readily absorbed by resilient sealing ma terial installed at each end of the rows of bricks.

In order to carry out the invention, it is advisable to string several, for example five, abutment bricks by means of a T-slot in their upper ends onto a suspension member which is in turn suspended on the supporting structure, for example, by means of suspension straps.

In other Words, the abutment bricks are threaded in rows consisting of clusters of several bricks which extend transversely across the firing gallery of the kiln on a suspension mounting, said rows of abutment bricks being spaced from each other longitudinally of the furnace. Each cluster of bricks can be lifted on its suspension memher out of the kiln upwards so that repairs can be carried out easily. Thanks to the ease with which the abutment bricks can be replaced, repairs to the furnace are greatly simplified and can be executed in much shorter time than in prior systems.

In ceilings according to the invention it is also necessary to space the fire-brick ceiling from the supporting structure of the furnace above it with the upper ends of abutment bricks and suspension members projecting into this space so that they dissipate heat rapidly to the air which may be blown through it. The suspension members on which the abutment bricks are hung are suspended by hanger bolts or straps from main supporting beams in the outer roof structure of the furnace. In this way, excessive heating of the ceiling support structure is avoided, thereby permitting operation of furnaces at temper-atures of, for example, 1400 C. for much longer periods of time without damage to the ceiling than has been possible with ceiling structures according to prior practice. In addition, by spacing the heavy metal support beams above the upper surface of the fire ceiling, the temperature differential between the upper and lower sides of the fire ceiling need not be so great when operating at these extremely high temperatures. This is due to the fact that the suspension members and hanger straps can be designed to hold up under higher temperatures and to dissipate heat much more rapidly than the heavy metal structural beams. Consequently, by reducing the temperature gradient within the bricks making up the fire ceiling, the expansion stresses within each brick are reduced substantially, making it possible to increase the operating temperature of the furnace without danger of damaging the bricks or the metal members by which they are suspended.

These and other advantages and objects of the invention will become more apparent from the description of one embodiment of the invention shown more or less schematically in the accompanying drawings, in which FIG. 1 is a perspective view of the roof portion of a section of a tunnel kiln showing a partially built ceiling construction according to the invention prior to installation of the outer roof of the furnace;

FIG. 2 is a longitudinal section taken on the line 2-2 of FIG. 1, but showing the roof completed;

FIG. 3 is a cross-section of the ceiling structure taken on the line 3-3 of FIG. 2;

FIG. 4 is a detail view on an enlarged scale of a section of the ceiling looking in the same direction as FIG. 2; and

FIG. 5 is a detail view looking in the same direction as FIG. 3 and showing two adjacent clusters of abutment bricks, one in elevation and the other in section.

In the drawings, the main supporting structure of the furnace including the upper part of its outer brickwork and side walls is indicated by the reference character A. Suspended within the furnace are a plurality of transversely extending rows of abutment bricks 1, which are disposed with their upper ends or heads projecting above the suspended fire ceiling, indicated generally at B. Pro- 'vided in each of said upper sections of the abutment bricks 1 is a T-shaped, upwardly opening slot in which is received a similarly shaped suspension member 2 of suitable length. Slots 10 are provided centrally of abutment bricks 1 so that said bricks hang with their centers of gravity vertically below the suspension member 2 on which they are mounted. Several (for example, five or six) abutment bricks 1 are threaded in clusters onto each suspension member 2. Said suspension member 2 is made of a single piece of heat-resistant cast metal, such as steel, which permits adequate dissipation of heat and avoids overheating of the suspension member. The heads of the abutment bricks 1 and the suspension members 2 project into a cooling space 3 formed between the fire ceiling B and the outer roof C of the kiln. Cooling air is passed through the air space 3, causing the heat to be dissipated from the abutment bricks and suspension members. Overheating of the ceilings is thus safely avoided.

Threading the abutment bricks 1 in clusters onto the suspension member 2 makes it possible to use abutment bricks that are thinner horizontally and deeper vertically, thus avoiding thermal stresses in the bricks and also reducing the amount of heat transfer to the metal ceilingsupport means, including the suspension members 2. FIG. 5 shows two clusters of abutment bricks. The bricks in the cluster 1a to the left, as viewed in the drawing, are strung on a suspension member 2a, While those in the cluster 1b to the right, which are shown in section, are mounted on an adjacent suspension member 2b. It will be noted that in case localized defects develop in the fire ceiling during operation of the furnace, it is possible to remove and replace one or more clusters of abutment bricks 1 Without dismantling an entire row of abutment bricks. Each suspension member 2 is secured by means of suspension straps 4 to a supporting structure 5, consisting of I-beams, each located directly above a row of bricks 1 and disposed transversely across the firing gallery. The rows of abutment bricks 1 are compressed together be tween the sidewalls of the firing gallery so that the joints between the bricks are sealed against leakage of air or gas in and out of the furnace. Because of the comparatively narrow width of the gallery, the heat expansion occurring in this direction is small.

Lengthwise of the firing gallery, however, the heat expansion is a multiple of that in the transverse direction because the furnace is many times longer than it is wide. Thus, While it is feasible to press the bricks together transversely of the furnace until they are rigid in order to maintain a seal between them, it is not possible, except where the furnace is relatively short in length and operated continuously at a uniform temperature, to make the ceiling rigid in the longitudinal direction. Even where the furnace is in continuous operation, the thermal expansion over the entire length of the furnace is so great that, after a relatively short period of operation, ceiling constructions of prior design have invariably developed leaks necessitating shut-down of the furnace for repair. Moreover, furnaces with such prior ceiling structures could not be shut down prior to a major overhaul because the bricks would loosen and fall due to contraction as the furnace cools.

In ceilingsaccording to the present invention, however, the individual bricks are permitted to expand and contract lengthwise of the furnace in such a way that excessive stresses between the brick and on the outer brickwork of the furnace are avoided. At the same time a good seal is maintained against leaks in the ceiling. To this end, rows of suspended bricks are interposed between the rows of abutment bricks as shown in FIGS. 2 and 4-. Each abutment brick 1 is provided adjacent its lower end with outwardly projecting shoulders 11, the upper sides of which form horizontal support surfaces 12. Each suspended brick 7, on the other hand, has outwardly projecting shoulders 13 adjacent its upper end which form downwardly facing horizontal engagement surfaces 14 on their undersides. Surfaces 14 of suspended bricks '7 overlap support surfaces 12 of abutment bricks 1 in a horizontal plane to form surface-to-surface seals which remain absolutely intact during expansion and contraction of the brick.

In addition, when the furnace is constructed, the suspended bricks 7 are laid so that expansion gaps x (FIG. 4) are provided between the opposite edges of their shoulders 13 and the adjacent sides of abutment bricks 1, and gaps y are left between the edges of the shoulders 11 of the abutment bricks and the adjacent sides of suspended bricks 7. Gaps x and y are shown exaggerated in size in FIG. 4 for purposes of clarity. For any particular spacing of the rows of abutment bricks, designated in FIG. 4

as dimension I, the lengths II and III of abutment bricks 1 and suspended bricks 7, respectively, must be chosen so that a gap x of the desired width may be provided on either side of the flanged part of suspended bricks 7. Similarly, dimensions IV and V of said abutment brick and suspended brick, respectively, likewise must be selected so as to leave gap y on either side of the depending portion of each suspended brick 7. Since abutment bricks I hang vertically from I-beams 5, their centers of gravity lie in the vertical planes which pass through suspension mem-bers 2 and I-beams 5 within each row of abutment bricks.

Expansion gaps x and y are desirably of such width that when the furnace is fired and brought up to its operating temperature, the bricks expand longitudinally of the furnace closing said gaps x and y. However, due to the fact that the horizontal engagement surfaces '12 and 14 of

bricks

1 and 7, respectively, can move horizontally relative to each other during expansion or contraction of the bricks without disturbing the surface-to-surface engagement between them, a good seal at the joints between bricks is maintained at all times. It will be noted, moreover, that while each of the

ceiling bricks

1 and 7 is permitted to expand and contract independently, they do not move bodily themselves, and their centers of gravity are therefore not displaced longitudinally of the furnace.

Absent such freedom to expand, each brick, as in the case of ceiling structures heretofore, tends to move the ones adjacent it. Thus, in a tunnel kiln which is 100* to 200 meters long, the total amount of expansion lengthwise of the furnace may be 1 to 2 meters, assuming the bricks expand 1% when the furnace reaches working temperature. If a ceiling this long were rigid, as in prior constructions, the furnace would be destroyed by the stresses and shifting of the brick caused by such expansion. On the other hand, in accordance with the present invention, the freedom of each individual ceiling brick to expand in place in the longitudinal direction allows the total lengthwise expansion to be taken up by the gaps between the individual bricks, thereby making feasible construction of ceilings of any desired length. In the transverse direction, on the other hand, since the ceiling is about 2 to 5 meters wide, it can be made rigid in this direction because the ceiling and outetr brickwork are able to withstand a total transverse expansion of only 2 to 5 centimeters. As may be seen in FIG. 3 abutment bricks 1 are desirably about half as wide transversely of the furnace as suspended bricks 7.

Furnace ceilings constructed in accordance with the invention are capable of lasting for long periods of time, even under intermittent operation, because the roof Works continuously lengthwise of the furnace upon heating and cooling without being damaged by the relative movement between the horizontal sealing surfaces of the bricks.

Such a structure departs drastically from prior roof constructions for tunnel furnaces where the generally accepted practice has been to make the fire ceiling rigid, both transversely and longitudinally, in order to prevent leakage. Such prior tunnel furnaces are brought to operating temperature once and then run for months without being cooled down. During this continuous operation, a single expansion takes place in the individual bricks of the roof. Since the roof remains at the operating temperature Without cooling off, the bricks stay in this expanded condition during the entire operation of the furnace. The present invention, therefore, is contrary to this long accepted and almost universal practice in the construction and operation of tunnel furnaces. Thus, the roof is purposely constructed so as to be flexible in the longitudinal direction in order to withstand the heretofore disastrous effects of alternating temperatures during operation of the furnace.

Purely by way of example, a fire ceiling in accordance with the invention makes possible the construction of tunnel kilns having a length L (FIG. 1) of 200' meters and a width W of 5 meters, or more than twice the length and Width of tunnel furnaces feasible heretofore. Consequently tunnel furnaces intended for operation at elevated temperatures of about 1000 C. to 1400 C. can now be constructed approximately four times the size of the largest such furnace possible before. Such larger furnaces are considerably more economical to construct and operate than the smaller tunnel kilns necessitated by prior ceiling constructions.

In a specific construction which has been found to be highly satisfactory, the [beams 5 (FIG. 4) are spaced approximately 625 mm. apart along the full length of the furnace with abutment bricks 1 suspended from each I- beam on four suspension members 2, each having from five to seven abutment bricks strung thereon. The length II of the upper end of each abutment brick 1 is 195 mm., while the parallel dimension IV across shoulders 11 at its bottom is 282 mm. Brick 1 is 350 mm. deep overall: 270 mm. from its top to support surface 12 and mm. from surface 12 to its underside.

The length III of the upper end of each suspended brick '7 in this particular instance is 425 mm., the length V of its depending portion is 340 mm., and its depth is 140 mm. Allowing for a small amount of leeway in the support structure for the ceiling, the suspended bricks 7 may be placed between adjacent rows of abutment bricks 1 on support shoulders 11 so as to leave an expansion gap x of about 4 mm. on each side, the expansion gaps y between the bottom portions of the bricks being about 3 mm. wide. The expansion gaps x and y are approximately equal to the amount of expansion of the bricks between the center of gravity of each abutment brick 1 and the center of gravity of the suspended brick 7 on either side thereof. Gaps x and y therefore close when the furnace is brought up to heat. A ceiling thus formed is capable of withstanding repeated heating and cooling between the ambient temperature and, for example, 1400 C. at its inner surface without damage to the ceiling itself or to the outer brickwork of the furnace. From the foregoing example it will be noted that the average length of both the abutment bricks 1 and suspended bricks 7 in the longitudinal direction of the furnace is approximately 300 mm. There will therefore be from about to nearly 700 alternating rows of abutment and suspended bricks in tunnel kilns of from 30 to 200 meters in length.

It will also be noted that the inner surface of the fire ceiling, where the greatest amount of heat is localized, is smooth and uninterrupted, thereby reducing variations in temperature along the firing gallery of the furnace. In addition, because the underside of the suspended bricks 7 are flush with the lower ends of abutment bricks 1 so that the space between the abutment bricks at the inner surface of the ceiling is filled, the heat from the furnace must travel a greater distance to the metal suspension members 2. Consequently, additional protection against excessive heat is provided these members.

Transverse-1y of the firing gallery, the vertical joints between the suspended bricks 7 are sealed with a mortar mixture. In this direction, both the abutment bricks 1 and the suspended bricks 7 which make up the ceiling are compressed together by flexible supports 9, which are located between the ends of the rows of

bricks

1 and 7 and the side wall of the furnace. Flexible supports 9 may consist for example of a mixture of asbestos fiber and clay or chamotte. According to Websters New International Dictionary, 1927, chamotte is a mixture of fire clay and burnt clay for making crucibles etc. As may be seen in FIGS. 3 and 5, the vertical joints between the bricks in the transverse direction are formed by mutually engaging substantially planar surfaces on the sides of the bricks which face transversely of the furnace.

As mentioned before, the present invention makes possible the use of thinner abutment bricks. Additional thermal insulation is obtained by interposing between the abutment bricks an insulating layer 6 of suitable thickness. In this connection, it is advisable to make the upper surfaces of suspended bricks 7 dish-shaped as illustrated in FIG. 2. Layer 6 may consist of fossil meal, diatomitic or other insulating material, which is bound with cement or clay. If this insulating layer in the individual longitudinal kiln sections is made to vary in thickness at the desired points, the temperature gradient in the kiln can be influenced by the ceilings themselves. This advantage is of particular importance, as owing to the buoyancy of high-temperature firing gases, the heat in tunnel kilns is localized below the ceilings, a condition difficult to control because of the insulating action of heavy ceilings having a low heat transfer coefiicient. In ceilings constructed according to the present invention, said control is easily possible by employing insulating layers 6 of different thicknesses.

In conclusion, it is desired to point out that ceilings constructed according to the present invention are sealed transversely of the firing gallery by means of vertical surfaces and mortar joints, whereas longitudinally of the firing gallery, seals are formed between overlapping horizontal surfaces which are capable of sliding with respect to each other in order to permit the bricks to work continuously as they expand and contract during heating and cooling without, however, disturbing the positions of the bricks relative to each other. In the vertical joints between the lateral edges of the bricks, the sealing faces may be ribbed, and labyrinth packings may be provided, if desired.

What is claimed is:

1. In a tunnel kiln, in which the length of the furnace is many times its width, and having a main supporting structure, a gas-tight ceiling construction comprising a plurality of abutment bricks hung from the supporting structure of the furnace by their upper ends and arranged in rows which are disposed transversely of the furnace and spaced from each other longitudinally thereof, a plurality of suspended bricks arranged in rows between said rows of abutment bricks and supported thereby, said abutment and suspended bricks having mutually engaging, substantially vertical and planar side faces facing transversely of said furnace, said side faces constituting the sole surfaces of engagement in the transverse direction, flexible means for maintaining said bricks in said transverse engagement to gas seal with each other, said suspended bricks having along both sides adjacent said abutment bricks downwardly facing, horizontal, engagement surfaces, said abutment bricks having correspondingly upwardly facing, horizontal support surfaces adjacent their lower ends disposed for cooperative engagement by said engagement surfaces of said abutment bricks, said horizontal engagement surfaces of each suspended brick being in continuous surface-to-surface gas sealing engagement with said horizontal support surfaces of said abutment bricks in the rows on opposite sides thereof, said abutment bricks and suspended bricks having mutually facing, substantially vertical side-surfaces adjacent said horizontal surfaces and facing longitudinally of the furnace, said bricks being disposed when said furnace is initially constructed such that said mutually facing, vertical side-surfaces are "spaced from each other by an amount substantially equal to the expansion of said bricks between their centers of gravity from row to row when said furnace is heated to operating temperature, so that the center of gravity of each individual brick remains substantially undisturbed in the longitudinal direction of said furnace, while said continuous surface-tosurface sealing engagement is maintained between said horizontal surfaces of said abutment bricks and said suspended bricks, respectively, despite relative movement between said horizontal surfaces during expansion or contraction of said bricks.

2. A ceiling construction for tunnel kilns as defined in claim 1, wherein said horizontal support surfaces of said abutment bricks are formed by outwardly projecting shoulders at the lower ends of said abutment bricks and said horizontal engagement surfaces of said suspended bricks are formed by outwardly projecting shoulders adjacent the upper ends of said suspended bricks, said mutually facing, vertical side-surfaces comprising the outer edge of a said shoulder on one of said bricks and the side of an adjacent brick in the next row, the under surfaces of said abutment and suspended bricks being flush in order to form a substantially smooth inner surface.

3. A ceiling construction for tunnel kilns as defined in claim 1, which further includes support means comprising suspension members, on each of which are hung a plurality of said abutment bricks to form a cluster thereof, each of said rows of abutment bricks comprising a plurality of said clusters, a support beam mounted in said furnace in spaced, parallel relation above each row of abutment bricks, and hanger means for suspending said suspension members from said beam.

4. A ceiling construction as defined in claim 1, wherein said abutment and suspended bricks are each approximately 300 mm. long in the direction of the length of a tunnel kiln of from 30 to 200 meters in lengths, said rows of bricks extending approximately 2 to 5 meters across the width of said tunnel kiln; said ceiling construction further including support means comprising suspension members, on each of which are hung a plurality of said abutment bricks to form a cluster thereof, each of said rows of abutment bricks comprising a plurality of said clusters, a support beam mounted in said furnace in spaced, parallel relation above each row of abutment bricks, and hanger means for suspending said suspension members from said beam; said horizontal engagement and support surfaces of said suspended and abutment bricks, respectively, being formed by overlapping shoulder-portions of said bricks which are shaped such that the under surfaces of said bricks are flush in order to provide a substantially smooth inner surface of said ceiling construction.

5. A ceiling construction as defined in claim 4, wherein the upper surfaces of said suspended bricks are dishshaped, and which further includes a layer of thermal insulating material of variable thickness disposed between the upper ends of said abutment bricks and within said dish-shaped upper surfaces of said suspended bricks for sealing and insulating said suspended bricks from above.

References (Iited by the Examiner UNITED STATES PATENTS 1,173,862 2/1916 Reilly -99 1,488,468 4/ 1924 Bigelon 110-99 1,517,291 12/1924 Jacobus 110-1 1,870,615 8/1932 Ellman 110-99 2,163,435 6/1939 Pollen 110-99 2,274,240 2/ 1942 Ladd 110-99 2,524,721 10/1950 Weber et al 110-99 2,664,837 1/1954 Banck 110-99 FOREIGN PATENTS 707,196 4/ 1931 France.

22,029 10/ 1907 Great Britain. 426,570 4/1935 Great Britain.

FREDERICK KETTERER, Primary Examiner.

Claims

1. IN A TUNNEL KILN, IN WHICH THE LENGTH OF THE FURNACE IS MANY TIMES ITS WIDTH, AND HAVING A MAIN SUPPORTING STRUCTURE, A GAS-TIGHT CEILING CONSTRUCTION COMPRISING A PLURALITY OF ABUTMENT BRICKS HUNG FROM THE SUPPORTING STRUCTURE OF THE FURNACE BY THEIR UPPER ENDS AND ARRANGED IN ROWS WHICH ARE DISPOSED TRANSVERSELY OF THE FURNACE AND SPACED FROM EACH OTHER LONGITUDINALLY THEREOF, A PLURALITY OF SUSPENDED BRICKS ARRANGED IN ROWS BETWEEN SAID ROWS OF ABUTMENT BRICKS AND SUPPORTED THEREBY, SAID ABUTMENT AND SUSPENDED BRICKS HAVING MUTUALLY ENGAGING, SUBSTANTIALLY VERTICAL AND PLANAR SIDE FACES FAACING TRANSVERSELY OF SAID FURNACE, SAID SIDE FACES CONSTITUTING THE SOLE SURFACES OF ENGAGEMENT IN THE TRANSVERSE DIRECTION, FLEXIBLE MEANS FOR MAINTAINING SAID BRICKS IN SAID TRANSVERSE ENGAGEMENT TO GAS SEAL WITH EACH OTHER, SAID SUSPENDED BRICKS HAVING ALONG BOTH SIDES ADJACENT SAID ABUTMENT BRICKS DOWNWARDLY FACING, HORIZONTAL, ENGAGEMENT SURFACES, SAID ABUTMENT BRICKS HAVING CORRESPONDINGLY UPWARDLY FACING, HORIZONTAL SUPPORT SURFACES ADJACENT THEIR LOWER ENDS DISPOSED FOR COOPERATIVE ENGAGEMENT BY SAID ENGAGEMENT SURFACES OF SAID ABUTMENT BRICKS, SAID HORIZONTAL ENGAGEMENT SURFACES OF EACH SUSPENDED BRICK BEING IN CONTINUOUS SURFACE-TO-SURFACE GAS SEALING ENGAGEMENT WITH SAID HORIZONTAL SUPPORT SURFACES OF SAID ABUTMENT BRICKS IN THE ROWS ON OPPOSITE SIDES THEREOF, SAID ABUTMENT BRICKS AND SUSPENDED BRICKS HAVING MUTUALLY FACING, SUBSTANTIALLY VERTICAL SIDE-SURFACES ADJACENT SAID HORIZONTAL SURFACES AND FACING LONGITUDINALLY OF THE FURNACE, SAID BRICKS BEING DISPOSED WHEN SAID FURNACE IS INITIALLY CONSTRUCTED SUCH THAT SAID MUTUALLY FACING, VERTICAL SIDE-SURFACES ARE SPACED FROM EACH OTHER BY AN AMOUNT SUBSTANTIALLY EQUAL TO THE EXPANSION OF SAID BRICKS BETWEEN THEIR CENTERS OF GRAVITY FROM ROW TO ROW WHEN SAID FURNACE IS HEATED TO OPERATING TEMPERATURE, SO THAT THE CENTER OF GRAVITY OF EACH INDIVIDUAL BRICK REMAINS SUBSTANTIALLY UNDISTURBED IN THE LONGITUDINAL DIRECTION OF SAID FURANCE, WHILE SAID CONTINUOUS SURFACE-TO-SURFACE SEALING ENGAGEMENT IS MAINTAINED BETWEEN SAID HORIZONTAL SURFACES OF SAID ABUTMENT BRICKS AND SAID SUSPENDED BRICKS, RESPECTIVELY, DESPITE RELATIVE MOVEMENT BETWEEN SAID HORIZONTAL SURFACES DURING EXPANSION OR CONTRACTION OF SAID BRICKS.