US2059176A - Rotary kiln - Google Patents

Description

Patented Oct. 27, 1936 PATENT OFFICE ROTARY KILN Ray 0. Newhouse, Wauwatosa, Wia, assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation of Delaware Application August 20, 1934, Serial No. 740,663

20 Claims.

flow of material through the kiln and do not sufficiently intercept the flow of hot gases through the kiln. In some kilns asheretofore constructed the chains are drawn taut across the kiln interior with the result that they either do not dip into the material at the bottom of the kiln when 15 it is rotated, or if they are so positioned as to dip into the material when at the bottom of the kiln, they do not hang down into the stream of hot gases when at the top of the kiln but leave a large opening free for the-flow of gases through the kiln without coming in contact with the chains. In either event they seriously obstruct the movement of material through the kiln.

In an attempt to correct this difliculty, chains have been suspended in kilns with slack with the undesired result that the chains when positioned at' the bottom of the kiln fold upon themselves and form a large tumbling mass which obstructs the normal flow of material through the kiln and results in excessive wear of the chains and of the kiln lining. Further, the slack chains so hang as to form a dense network near the bottomof the kiln, leaving the top of the kiln open and permitting the hot gases to pass along 35 the top of the kiln without contacting with the 1 40 in the material being treated, it has been necessary in kilns ofwthis type as previously constructed to install an excessive amount of chains to effect the required transfer of heat to the material being treated.

It is the general object of this invention to overcome the difliculties previously met with in chain kilns by providing an arrangement of chains for'a rotary kiln which functions efliciently in transferring heat from the hot kiln gases to the material being treated. .9 v

A more specific object of the invention to this end is to provide an arrangement of chains in a rotary kiln whereby the greatest concentration of suspended-chains occurs at the top of the kiln in the normal path of the hottest kiln gases.

when in suspended position in the kiln tend to Another object of the invention is to provide a chain system for a rotary kiln in which the density of the suspended chain curtain decreases from the top toward the bottom of the kiln.

Another object of the invention is to provide 5 a chain system for a rotary kiln in which the chains are so suspended as to provide a free space just above the bottom of the kiln to induce the hot kiln gases to flow directly over the material in the bottom of the kiln.

Another object of the invention is to provide a chain system for a rotary kiln in which the chains are so suspended that when they are at the bottom of the kiln, they conform to the interior surface thereof to permit the material being treated to advance over them through the kiln.

Another object of the invention is to so suspend the chains in a rotary kiln as to prevent tumbling thereof on the bottom of the kiln to thereby avoid excessive wearing of the chains and of the kiln liner.

Another object of the invention is to provide a chain system for a rotary kiln including the combination of a plurality of long relatively heavy chains so suspended as to hang into the lower portion of the kiln, and a. plurality of short rela- 5 tively light chains so suspended as to form a dense chain curtain near the top of the kiln.

A further object of the invention is to provide a chain curtain for a rotary kiln formed of units, each unit comprising sequentially arranged chains in a transverse plane of the kiln and successive units being displaced angularly to form a composite interlacing curtain.

A further object of the invention is to provide a novel chain attachment block for a chain kiln.

In practicing the improvements of the present invention, the chains in a kiln are arranged in a series of chain units disposed in spaced transverse planes of the kiln. Each unit is formed by a plurality of relatively, heavy chains of different lengths, each chain being attached at its ends to the interior of the kiln at points spaced circumferentially and each chain being of length equal to the circumferential distance between the points of attachment of its ends. The chain units are each formed with chains arranged sequentially around the kiln and successive units are displaced angularly in such manner that the chains form a continuous interlaced network or curtain, the length of the chains being so chosen that the chain curtain formed by them is of progressively less density toward the bottom of the kiln. At the cooler end of the kiln additional relatively short light-weight chains are provided to 01' great density near the Figure 1 is a view in side elevation of a rotary kiln illustrating diagrammatically the disposition therein of a chain system embodying the present invention;

Figure 2 is a development showing the interior of the upper or inlet end portion of a rotary kiln and illustrating diagrammatically the position at which the ends of the chains are attached to the kiln interior in accordance with the present invention; 1

Figure 3 is a view in cross section of a kiln taken on the plane represented by the line III-III in the development of Figure 2 and showing the single chain unit in that plane; I

Figure 4 is a view in cross section taken on the plane represented by the line IV-IV in the development of Figure 2 and showing only the single chain unit disposed in that plane; Figure 5 is a view in cross section taken on the plane represented by the line VV in the development of Figure 2 looking in the direction of the arrows and showing all of the chains of the first chain set;

Figure 6 is a view in cross section taken on the units in the plane represented by the line VI VI in the development of Figure 2 looking in the direction of the arrows andshowing all of the chains of the first chain group;

Figure 7 is an enlarged detailed view in cross section of an attaching block for securing the chain ends to the kiln interior, taken on the plane represented by the line VII-VII in Figure 8;

Figure 8 is a fragmentary view of the attaching block partly in side elevation and partly in longitudinal section taken on sented by the line VIII-VIII of Figure I;

Figure 9 is a view similar to Figure 7 of an attaching block for use in the hotter portion 01' the kiln and taken on the plane represented by the line IX-IX of Figure 10; and

Figure 10 is a view similar to Figure 8 showing the attaching block illustrated in Figure 9 partly in side elevation and partly in longitudinal section taken on the plane represented by the line XX of Figure 9.

Referring more particularly to the drawing, the rotary kiln I illustrated in Figure 1 by way of example as a practical structure embodying the present invention, is of the well known type used in the manufacture of Portland cement or the like. A kiln of this type is usually divided generally into a burning zone at the lower end thereof and a drying zone at the upper end. The present invention is particularly concerned with the drying zone of the typical kiln illustrated, although it is to be understood that the invention may be applied to rotary kilns of other types or to rotary drying drums used separately for drying material.

- As shown in Figure 1', the typical rotary kiln l comprises essentially a rotatably mounted cylindrical drum or shell 2 disposed in inclined'position in the usual manner and arranged to receive wet material to be treated from -a spout I which enters the inlet end 4 of the kiln. For providing hot gases to dry and burn the material within the kiln, a removable firing hood 8 provided with a burner l is appliedto the discharge end I of the plane reprethe kiln. The firing hood 8 is arranged in well known manner to cause a flow of hot gases longitudinally through the kiln shell 2 from the discharge end 8 thereof to the inlet end 4, where the spent gases are collected in a housing 5 from which they may be conveyed away to be discharged by a chimney or the like in the usual manner.

The wet material, for example, wet cement slurry, which enters the inlet end 4 of the kiln through the spout I, is caused to advance through the kiln in the usual manner by slowly rotating the kiln shell by means of a ring gear 9 that encircles and is attached to the shell and which is driven by a meshing pinion I0 rotatably mounted in a supporting bearing I I. I

In progressing through the kiln shell 2, the wet material engages in the upper or drying and of the shell with the' chains of a chain system embodying the present invention and is elevated thereby into contact with the hot kiln gases. The extent of the entire chain system in the kiln shell I is indicated in Fig. 1 by the bracket II. The material to be treated enters .the kiln in wet and cool condition and is first acted upon by the chains in the zone of the chain system that is indicated by the bracket I3 in Fig. 1. This zone of the system includes 'a large number of relatively light short. chains in addition to sets of longer relatively heavy chains arranged around the inner circumference of the shell 2. In passing through the zone It of light and heavy chains, the

material being treated is dried and heated to such an extent that its cooling action upon the chains is no longer sufiicient to prevent light chains in the chain system from being quickly destroyed by the hot kiln gases. Consequently, in the remaining zone of the chain systemLindicated by the bracket ll, only the heavier chains are utilized.

After the material being treated has passed through both of the chain zones i3 and ll of the chain system II, it is first calcinated and then clinkered in the burning zone of the kiln and subsequently discharged from the discharge end 8 of the shell 2 through the firing hood 6 in the usual manner.

In the process of treating the wet material in the drying zone of the kiln containing the chain system of the material be elevated by the chains to the top part of the kiln in order to bring it into contact with the hottest kiln gases which normally pass along the kiln Just beneath the top of the shell. Further, it is desirable that as much as possible of the chains be exposed to the hot gases in the top portion of the kiln in order that the chains may be heated for subsequently conveying the heat thus absorbed to the material at the bottom of the kiln when they are rotated into contact with it. It is also desirable that the flow of the hot gases along the top portion of the kiln 2 be intercepted and retarded in such manner as to tend to force the hot gases downward into conl2, lt' isdesirable that as much as possible tact with the material at. the bottom of the kiln.

To accomplish these chain system are arranged, in accordance with results the chains ofthe the present invention 'as shown in the cross sec- I kiln are so arranged that they conform to the interior surface of the kiln when they are resting on the bottom thereof in such manner as to permit the material being treated to advance over them through the kiln without being unduly obstructed.

In suspending the chains in this manner in accordance with the present invention, the chains are arranged, as illustrated in Fig. 2, in a plurality of circular chain units each disposed in a transverse plane of the kiln. Each chain unit includes a plurality of chains of different lengths suspended from the interior surface of the kiln shell 2 in such manner that when adjacent units are suitably displaced angularly relative to each other, the desired arrangement of chains shown in Figure 6 is obtained.

Referring particularly to Figures 3 and 4 which show similar individual chain units 5| and 55 displaced 180 relative to each other, the particular arrangement of chains shown for practicing the invention includes in each chain unit two long heavy chains l5 of equal length connected at their ends to attachment points spaced at 135 and one shorter heavy chain l6 attached at its ends to attachment points spaced at 90'. As the total of the attachment point spacing angles constitutes 360, the ends of the three chains are connected to three common suitably spaced attachment points in such manner that the chains of the unit are arranged in sequence forming a continuous chain circle around the kiln interior. In order that the chains may conform to the inner surface of the kiln when resting on the bottom thereof, each of the chains i5 and i5 is formed of length approximately equal to the circumferential distance between the attachment points for its ends.

For convenience in laying out the positions for the chain attachment points in the kiln and in providing suitable securing means for the chain ends, the chain units of the chain system are arranged in sets, each set being indicated by the numeral 2| in Figure 2. The successive chain units of each set 2| are progressively displaced angularly by an angle that is a common divisor of the angular spacing of the chain end attachment points of each unit. In the particular arrangement shown in the drawing, the successive chain units of each chain set 2| are displaced progressively through an angle of 45, whereby all of the end supporting points of both the 135 and the 90? chains occur in a series of longitudinal lines spaced at 45 upon the interior of the shell 2. With the adjacent chain units displaced through 45, a complete cycle of angular displacement iseffected in eight successive displacements, consequently eight successively displaced chain units 5| to 58 are grouped together in forming one complete chain set 2|. The composite chain curtain formed by the first chain set 2| of eight chain units is shown in Figure 5.

As the attachment points for the ends of the chains in the units 5| to 58 of each set 2| are arranged in alinement on longitudinal lines 'spaced at 45 intervals, it is convenient to provide a series of longitudinally disposed attachment blocks I9 arranged circumferentially of the kiln and spaced at 45 intervals for receiving the ends of the chains of each chain set 2|, as indicated diagrammatically in Figure 2 of the drawing. In the zone l3 at the upper end of the kiln containing both light and heavy chains, the attachment blocks l9 also serve to secure the ends of short light chains extending between adjacent blocks. I

The points of attachment of the ends of the heavy chains l5 and It to the blocks l9 are indicated in Figure 2 by the centrally disposed small circles '40. For instance, in the first chain'set 2| the attachment point at position 14 for the chains ll of the first chain unit 5|, shown at the top of the kiln shell in Figure 3 is represented in Figure 2 by the circle 40 in the plane indicated by the line IIIIII at the intersection thereof with the line 50-60, which is designated attachment position 14 in this figure also. The points 40 above and below position 14 on the line -60, at attachment positions II and II respectively in the plane IIIIII of Figure 2, are each spaced therefrom through an angular distance of 135 and these points at positions II and TI are spaced from each other through an angle of completing the circle of the first chain unit 5|.

As shown in Figure 3, the two long heavy chains l5 of the first chain unit 5| are both attached at one end to the attachment block at position 14 and are attached at their other ends respectively to the attachment blocks at positions H and 11, the short heavy chain it being connected betweenthese latter two blocks. In Figure 4, the short heavy chain It of chain unit 55 is shown suspended at its ends from attachment blocks at positions 13 and I5 and the two long heavy chains l5 are respectively suspended ment point 40 to which the ends of the chains l5 of the chain unit 55 in the plane IV--IV are connected and which corresponds to the attachment point of the chains l5 of chain unit 5| at position 14 at the top of the kiln shell in Figure 3, is displaced therefrom through four increments of 45 or a total of bringing it to position I8 at the bottom of the kiln, as shown in Figure 4. In the composite set 2| of the eight chain units. 5| to 58 shown in Figure 5, it may be seen that the longer chains l5 form the portion of the network near the bottom of the kiln and that the shorter chains l5 cooperate with the long chains l5 and with the light chains II to form the denser network near the top of the kiln.

To effect angular oifsetting of the chains of adjacent chain sets 2|, the chain sets are arranged in groups 22 of three sets each, each set 2| of chain units in a group 22 being displaced 15 relative to the adjacent chain s'et 2|, whereby the three sets 2| form a complete cycle for the group. The composite curtain of chains formed by one group 22 of three sets 2| is shown in Figure 6.

In order that the chains of adjacent chain groups 22 may be angularly offset, each chain group 22 is displaced angularly through an angle of 3 relative to the adjacent chain group. This is accomplished by positioning the attachment blocks IQ of the first chain set 2|, in one group at an angle of 18 instead of 15 relative to the blocks IQ of the last chain set 2| in the previous group 22 as may be seen by referring to Figure 2. To constitute a complete kiln cycle 25, a total of five groups 22, each displaced 3 relative to the adjacent group, is required.

In the portion of the chain system l2 indicated by the bracket l3 in Figure 1 the heavy chains 5 II and it are supplemented by a plurality of light chains l1 which are connected at their ends to adjacent attachment blocks i9 spaced at 45 and are of length equal to the circumierential distance between these blocks. These chains 10 are connected to the. blocks I 9 at attachment points which are indicated in Figure 2 by the small circles 42 along the edges of each block. In practicing the invention, the light chains H are ordinarily positioned closer together than is indicated by the attachment points 42 shown in Figure 2, usually being placed in such manner that they cover substantially the entire inner surface of the kiln when they are resting on the bottom thereof.

The position taken by the light chains ii is illustrated in Figures 3, 4, 5 and 6 oi' the drawing. Figure 6 shows clearly the manner in which the light chains ll cooperate with the heavy chains l5 and It to form a composite chain net- 2 work of great density at the top portion of the kiln and of diminishing density toward the bottom of the kiln. This dense network of chains lifts a large amount of the material being treated into contact with the hot kiln gases at the top 30 01 the kiln as the kiln is rotated and constitutes a barrier tending to force the kiln gases down- 35 tained than by the previously used chain systems, and the material of thechains is operated atv much greater drying efficiency than that of chains as heretoiore utilized. The attachment blocks l9, which are shown in 40 detail in Figures 7 and 8, each comprises a cast or forged metal block provided with end flanges 24 for receiving attaching bolts 25 by means-.0! which the block may be rigidly secured to the inner surface of the kiln shell 2. The blocks I9 45 are of such height that they extend inwardly -i'rom the shell 2 a suflicient distance to provide space {or a lining I8 01' nrebrick or other suitable material within the kiln shell 2. Each block is formed hollow with a longitudinally extending 50 recess or cavity 29 in its lower portion adjacent to the shell 2. The inwardly extending portion 01' each block I9 is provided with a longitudinal slot 3.9 for receiving bolts that serve to secure the ends or the heavy chains to the block. Trans- 55 verse' webs 6| are provided 'in the cavity 29 of each block to strengthen it and openings 21 are formed-through the transverse webs to permit movement therethrough of the heads of the bolts 29. Beneath thev openings 21 a central longitudi- 80 nal web 23 is disposed in the cavity 28 to act as a stop for the heads of the bolts 29 to prevent them dropping into the cavity 26. Rectangular notches or depressions 38 are formed at spaced positions in the body or the block above the web 65 29 for receiving the square heads of the bolts 29 in order to position them in the transverse planes of the chain units. Each bolt 29 is pro-' vided at its outer end with a clamp member 3| having opposed hookrportions 32 disposed to pass lo-over the endirlinks'oi theheavy chains IE or l6 and to engagei'n seats 39 in the outer surface 01' the block ll 'tofsecurely retain the chain ends .;when then :1 t e endskof the bolts 29 are 1; For nthe sides or each block I 9 are provided with spaced recesses 33 each adapted to receive the end link of a chain. The chain end links are secured in the recesses 33 by means or longitudinally extending rods or bolts 35 passing through longitudinal 5 openings 34 in the block I9 and through the end links within the recesses. As shown in Figure 8, the recesses 33 for receiving the end links of the chains I! are closely positioned in such manner as to receive a sumcient number of the light 10 chains H to substantially cover the entire inner surface oi the kiln. Although the attaching points for the light chains i! are indicated diagrammatically in Figure 2 by the small circles 42 as being in the planes oi. the attachment points 15 49 of the large chains for the sake of simplicity in illustration; the link receiving recesses 33 are not necessarily positioned in definite relation to the clamp members 3| but may be arranged entirely independent thereof as shown in Figure 8; 20

In the portion of the chain system l2 indicated by the bracket l4 in Figure 1 in which no light chains I'I are used, the attachment blocks 29 shown in Figures 9 and 10 having means for attaching heavy chains only are utilized. As 25 shown in Figures 9 and 10. each block 20 is similar in general to the blocks l3 shown in Figures 7 and B but is not formed as high as the block i9 as it is not necessary to provide space for the attachment oi chains to its sides, and consequentvly the longitudinal interior recess 36- thereof is not as large as the recess 29 in the block l9.

As in the case of the blocks I3, each block 29 is provided with end flanges 24 and securing bolts 25 and with a longitudinal slot 39 communicating with the recess 39 for receiving the bolts 29 which secured the clamp members 3| ior receiving the end links of the heavy chains II and I6. Beneath the slot 39 a longitudinally disposed web 31 is provided for engaging theheads ot the bolts 40 29 to retain them within the block. Although the chain system disclosed herein has been shown applied only in one specific way to one type 01 kiln, it is to be understood that chain systems embodying the invention defined in the subjoined claims may be applied by thoseskilled in the art to other types of kilns or similar apparatus without departing from the spirit of the invention.

It'is claimed and desired to secure by Letters Patent:

1. A chain system for a rotary kiln, comprising a plurality of' relatively light chains suspended within the shell oi! the kiln to hang in a dense mass near the top thereof to intercept the hot kiln gases in the upper portion of the kiln, and a plurality of relatively heavy chains suspended to cooperate with said light chains to forms. composite chain curtain of progressively decreasing density from the top to the bottom of the kiln.

2. A chain kiln, comprising a rotatably mounted drum, a plurality of chains suspended within said drum, said chains being arranged to form a curtain therein of great density at its upper 5 portion and of decreasing density downwardly therefrom terminating at an open lower portion just above the material being dried in the bottom of the drum, whereby hot gases passing through said drum engage said chains at the up- 7 per part thereof and are urged downwardly thereby into contact with the material in the bottom of the drum.

3. A rotary kiln for heat treating material, comprising a rotatably mounted drum, means for I p v 2,050,170 feeding material to be treated into oneend of said drum for advancement therethrough, means for passing heated gases through said drum, and a plurality of chains attached to the interior of said drum for elevating said material into contactthe hot gases over the material being treated at the bottom of the drum, said chains at the bottom of the drum substantially conforming to the inner surface thereof to permit free progression of the material thereover through the kiln.

4. A chain kiln, comprising a rotatably mounted drum, and a chain unit disposed in a transverse plane of said drum, said chain unit including one chain attached at its ends to the interior surface of said drum points spaced at 90 thereon and two chains each attached at one end to the respective en'd attachment points of said 90 chain and attached at their other ends to a common attachment point midway between and diametrically disposed with respect to said end attachment points of said 90 chain. a

5. A chain kiln, comprising a rotatably mounted drum, and a circular chain unit disposed in a transverse plane of said drum, said chain unit including one chain attached at its ends to the interior surface of said drum at attachment points spaced at 90, said chain being of length equal to the circumferential distance between said attachment points, and two chains each attached at one end tothe respective end attachment points of said 90 chain and at their other ends to. a

- common attachment point disposed 135 from said 90 attachment points, said 135 chains each being of length equal to the circumferential distance between the attachment points of its ends.

6. A rotary kiln comprising a rotatably mounted tube that constitutes a burning zone and a drying zone, a plurality of chains suspended within said drying zone, said chains beingattached at their ends to the inner surface of said tube and disposed in circular units in spaced transverse planes, each transverse plane chain unit comprising one chain attached at its ends at points spaced at 90 and of length equal to the circumferential distance between said points of attachment and two chains each attached at one end to an end attachment point of said first chain and at the other end to a mutual attachment point midway between said first attachment points and each chain supported at its ends at points spaced 90 upon the interior of the tube and two chains supported at their ends at points spaced 135 forming a continuous chain unit around the tube, the said chains being of lengths equal to the circumferential distances between the supporting points of their ends, said circular chain units being arranged in sets with the-chains of adjacent units displaced angularly but with their points of support in longitudinal alinement to facilitate attachment thereof to the tube, said sets of chain units being displaced angularly to misaline them and arranged in groups, the sets of each group being displaced successively an equal amount and said groups being displaced angularly to dispose the sets of adjacent groups in alternate relationship.

8. A rotary kiln for heat treating material, comprising a rotatably mounted drum, a plurality of equally spaced attachment members secured upon the interior of said drum, and a plurality of heat transferring members arranged in circular units, each unit comprising a plurality of chains each attached at each end to noncontiguous attachment members forming a sequential arrangement, said units being displaced angularly relative to each other to-form a composite chain set.

9. In a chain kiln, the combination with a 1'0- tatably mounted drum, of a plurality of attach-' ment blocks for chain ends mounted in spaced re-,

lation upon vthe interior surface of said drum; each of said attachment blocks comprising a body portion having a longitudinally extending bolt receiving slot, bolt head receiving sockets in spaced positions along the inner edge of said slot, chain and link receiving sockets arranged along the sides of said body, and longitudinal passages intersecting said link receiving sockets; a plurality of bolts disposed insaid longitudinal slot with their heads engaging predetermined ones of said bolt head receiving sockets, chain end clamping members carried by said bolts in position to extend through chain end links and clamp against said body portion to retain said links, and rods extending through said longitudinal passages and said link receiving sockets in position to pass through chain end links therein to retain them.

in said sockets. v

10. In a rotary kiln, the combination with a rotatably mounted kiln shell, of a. chain system mounted therein, comprising eight chain attachment blocks secured to the inner surface of the kiln shell and arranged circumferentially thereof at 45 intervals, and eight chain units arranged in parallel planes and carried by said attachment blocks each chain unit including a chain of length equal to the circumferential distance between blocks spaced at 90 said chain being attached at its ends to blocks so spaced, and two chains of length equal to the circumferential distance between blocks spaced at 135 each attached at one end to one of the blocks supporting the said 90 chain and each attached at the other end to a common block positioned at 135 from said 90 spaced blocks, said chains of each unit lying in a transverse plane of said I kiln shell and the chainsof adjacent units being displaced angularly successively to constitute a composite chain system.

11. A rotary kiln chain system, comprising a,

plurality of chain attachment blocks disposed in equally spaced relation on the inner surface of a rotary kiln shell defining a series of kiln segments therebetween, a plurality of light weight chains of length equal to one of said segments each disposed to subtend one of said segments with its ends attached to the attachment blocksdelimiting said segment, a plurality of heavy weight chains of length equal to two of said kiln segments each disposed to subtend two segments with its ends attached to the attachment blocks delimiting said two segments, and a plurality of heavy weight chains of length equal to three of said kiln segments each disposed to subtend three segments with its ends attached to the attachment blocks delimiting said three segments.

12. In a rotary kiln chain system, the combination with a rotatable kiln shell, of a plurality of chain attachment blocks disposed on the inner surface of said rotatable kiln shell at positionsof the kiln, a plurality of chains of length equal to the circumferential length of two kiln segments each attached at its ends to attachment blocks spaced at in manner to hang in generally horizontal position across the upper portion of the kiln to form a dense chain curtain therein, and a plurality of chains of length equal to the circumferential length of three kiln segments each attached at its ends to attachment blocks spaced at in manner to hang in generally vertical position to the bottom of the kiln at the sides of the center thereof and in generally horizontal position across the kiln below its center to form a chain curtain in the lower position of the kiln defining a relatively narrow unobstructed passageway along the bottom of the kiln.

13. In a rotary kiln chain system, a rotary kiln shell, a plurality of chain attachment blocks disposed on the inner surface of the rotary kiln shell at positions spaced 45 circumferentially and defining included kiln segments therebetween, a plurality of chains of length equal to the circumferential length of two of said included kiln segments each attached at its ends to attachment blocks spaced at 90 to hang in generally horizontal position across the upper portion of the kiln, individual chains being disposed in different planes and at different angular positions to form a dense chain curtain in the upper portion of the kiln, and a plurality of chains of length equal to the circumferential length of three of said-included kiln segments each attached at its ends to attachment blocks spaced at 135 to hang in generally horizontal position across the kiln below its center or in generally vertical positions at the sides of the kiln center from the top to the bottom thereof, individual chains being dis.- posed in different planes and at different angular positions to form an arched chain curtain in the lower portion of the kiln defining a relatively narrow unobstructed passageway along the bottom of the kiln shell.

14. In a rotary kiln having a rotatable kiln shell, a chain system comprising a plurality of chain attachment blocks arranged on the inner surface of the rotatable kiln shell in circumferentially spaced relation and defining therebetween equal included kiln segments defining an acute angle, a plurality of chains equal in length to the,

lar positions to form a dense chain curtain. in

. the upper portion of the kiln, and a plurality ment blocks disposed in ispaced relation on the 1 inner surface of said rotatable kiln shell, a plurality of light weight chains of length substantially equal to the circumferential distance between adjacent attachment blocks each attached at its ends to adjacent attachment blocks in such manner asto hang when in the upper part of the kiln in generally horizontal position near the top of the kiln, a plurality of heavy weight chains of length substantially equal to the circumferential distance between alternate attachment blocks each attached at its ends to alternate attachment blocks in such manner as to hang when in generally horizontal position across the upper portion of the kiln, and a plurality of heavy weight chains of length substantially equal to the circumferential distance between each third attachment block each attached at its ends to two attachment blocks spaced by three included blocks in such manner as to hang when in generally horizontal position across the kiln below its center and to hang when in generally vertical position into the lower portion of the kiln at one side of the center to define a narrow unobstructed passageway for hot gases along the'bottom of the kiln shell.

16. In a rotary kiln of the type having chains suspended therein, a chain supporting block attached to the inner surface of said kiln said block having openings along its sides for receiving the end links of chains, and a rod disposed longitudinally of said block and adjacent said openings in position to pass through chain end links to retain them within said openings.

17. A rotary kiln comprising a rotatably mounted kiln shell, a plurality of chain attachment blocks disposed longitudinally of said kiln in clrcumferentially spaced relation on the inner surface ofsaid kiln shell, said blocks having openings for receiving the end linksof chains, a plurality of chains disposed with their end links extending into said openings in said blocks, and rods passing through said chain end links within said openings to secure said chains to said blocks.

18. In a chain kiln, means for attaching the ends of chains to the inner surface of the kiln, comprising attachment blocks arranged in spaced relation upon the inner surface of the kiln, each of said blocks having means arranged centrally along the face of its inwardly extending portion for securing the ends of long chains and having openings along the sides of its inwardly extending portion for receiving the end links of short chains, and means for retaining chain end links within said side openings.

19. In a chain kiln, means for attaching the ends of chains to the inner surface of the kiln, comprising a plurality of attachment blocks arranged in spaced relation upon the inner surface of the kiln, each of said blocks having openings along its sides for receiving the end links of chains, and means within said blocks for retaining chain end links within said openings.

20. In a. chain kiln, the combination with a rotatably mounted shell, of a plurality of attachmnt blocks each adapted to engage the ends of a plurality of chains, said attachment blocks bing arranged upon the inner surface of said shell in circumi'erentially allned rows, the blocks of each row being equally spaced angularly and said rows of blocks being disposed in groups with the rows of each group displaced angularly relative to each other and with the groups displaced 5 angularly relative to one another.

RAY C. NEWHOUSE.

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