US3024538A

US3024538A - Aggregate drying apparatus

Info

Publication number: US3024538A
Application number: US732962A
Authority: US
Inventors: Walter M Madsen
Original assignee: Baldwin Lima Hamilton Corp
Current assignee: Baldwin Lima Hamilton Corp
Priority date: 1958-05-05
Filing date: 1958-05-05
Publication date: 1962-03-13
Anticipated expiration: 1979-03-13

Description

March 13, 1962 w. M. MADsEN AGGREGATE DRYING APPARATUS Filed May 5, 1958 WAL TER M MAosE/V,

INVENTOR. WHA/VN Mc MAN/GAI.

3,024,538 AGGREGATE DRYENG APPARATUS Walter M. Madsen, Arcadia, Calif., assigner to Baldwin- Lima-Hamilton Corporation, Philadelphia, Pa., a corporation ot Pennsylvania Filed May 5, 1958, Ser. No. 732,?62 8 Claims. tCl. Sii- 135) This invention relates generally to drying equipment and relates `more particularly to apparatus for drying various types of aggregates used in the paving industry and the like.

While the present apparatus has particular utility in the heating and drying ot aggregates, such as rock, sand, dust, etc. used in the asphalt paving industry, and is shown and described in connection with drum type driers used in said industry for the heating and drying of such aggregates, it is to be understood that its utility is not confined thereto.

In the production ot bituminous tbound paving mixtures, the aggregate, which may range from two and onehalt inch rock downwardly to sand and rock dust, is `dried in a cylindrical type drier which rotates and drops the rock and sand through the hot gases. Such driers are usually ot the counter-how type, that is, the rock and sand are `fed into one end of the drier land the tire is directed into the opposite end of said drier. Thus, the aggregates pass through the cylindrical shell in one direction and the hot gases from the tire pass through in a directly opposite direction. The driers are usually pitched in an inclination downwardly toward the tirebox end. In other words, the aggregate ingoing end of the drier shell or kiln is higher than the discharge end.

In such driers various forms and shapes of litters or buckets are used and are so placed on the shell interior that in combination with the rotation of the shell or kiln, the litters or buckets raise the material to the top of the shell and throughout this portion ot the shell movement, the buckets or litters carry the material upwardly, dropping same when the angle ot repose of the material contained within or on the litters or buckets is such fas to cause such material to tall ott. This `falling ott action, once it starts, becomes continuous with turther rotation ot the shell resulting in an action that is termed in the parlance ot the trade as aggregate curtains.

Regardless ot the type of litters used in driers of the yabove described character, the action of these litters is generally about the same. Some litters may tend to hold the aggregate a little longer in its circular elevation conforming to the kiln `or shell interior diameter and thereby cast the aggregate therefrom a little further toward the down side of the shell, but in general, the litters conform in manners inherent in their basic concept which is specically to block oft a given amount ot material when they are positioned at the bottom ot the shell and as the rotation of the shell to which the litters are attached continues the aggregate thus caught by the litters is carried upward and gradually dropped.

The aggregate is ted into the drier as fa composite, such composite consisting of rock, sand, rock dust, or other tine material. It naturally follows that these various aggregates in a composite combination continue their passage through the shell, being lit-ted by the litters and dropped through the hot gases, and as the shell is inclined downwardly toward the tired end, these aggregates move to the low end ot the shell in a continuing composite manner and are discharged from said low end. As the aggregates approach the lire, they naturally become hotter and, therefore, drier.

As is well known in the art, these aggregates as ted into the drier `may contain considerable moisture. Such moisture content may be seven, eight or nine percent and are States Patent known lto run as high as 15% and sometimes even higher, depending upon the type ot aggregate being ted and the point from which the aggregate may have been taken. For example, sand freshly dragged out of the river, to gether with silt and clay, could contain a very high percentage ot moisture if it had no opportunity to air dry tor a substantial period prior to being ted into the drier. As the aggregates, coarse and tine alike, are of substantially the same specific gravity more or less, they pas-s through the shell together, there being no appreciable segregation occurring as the result ot the lifting of the aggregate by the litters and the dropping olf same theretrom as said litters move through their circular path.

Should there be any moisture present in the aggregates, the mixture, which includes the asphalt etc., sticks to the implements used in connection with the preparation and laying ot the asphalt paving so that it is absolutely necessary tor the aggregate to be practically bone dry. The problem of producing such a dry condition of the aggregate with present types ot driers has, as far as I am aware, not been solved and it is, therefore, an object ot the present invention to provide a drier that will remove substantially -all of the moisture from aggregate material supplied thereto so that when said material is discharged therefrom, it has the required degree of dryness.

The difficulty encountered in drying composite aggregates apparently is due to the tact that the sands and fines, ranging in size upwardly to a quarter inch and even slightly larger, are robbers of heat. These aggregates, and particularly the finer components thereof such as the 200 mesh rock dust and coarser material up to and including sand, steal the heat from the fire or flame or hot gases and reach fantastically high temperatures while at the same time act as an insulator which prevents the coarser stone from receiving the direct eilect of the heat. It is well known that a rock ot a given size, say a rock having a weight of one ounce and a surface area perhaps of one square inch, could be broken into particles ot sand which would have a surface area many thousands of times larger than the rock from which it was made. As pointed out above, aggregate mixtures used in bituminous paving material may consist of various grades ot rock, from a quarter inch to three-quarters inches, and even 'as large as two and one-halt or three inches in heavy Ibase mixtures. The sand in such aggregate mixtures may range from as low as 15% or 20% upwardly to a high of 50% to 55% ot such mixture. That is, the sand and fines of an aggregate composite combination may go `from `a low of 15% to a high of 50% ot the total mix. Probably the average normal sand content of the aggregate mix would run in the neighborhood of 35% ot `the total mix contained in the average bituminous specifications.

When using the term sand herein, it is intended to include various ranges tot fines which may be contained in the sand and these will run from micron sizes up to six or eight mesh.

As above stated, the sand and fines are stealers of heat and insulators, creating a fog within the kiln or shell which prevents the larger pieces ot gravel and rock from being adequately dried. It is, therefore, another object ot the invention to provide drying apparatus which will thoroughly dry all of the grades of material ot such composite aggregates.

Another object ot the invention is to provide apparatus of this character which will separate the sand from the gravel and rock in the kiln so that t-he rock receives the -full effect of the blast of the tire, out ot the presence of the stealer ot heat.

Still another object of the invention is to provide apparatus of this character which will so segregate the sand posite aggregate in the kiln that said larger particles Will be uninsulated and will be thoroughly dried.

It is a further object of the present invention to provide apparatus of this character that will function properly over relatively long periods of time and will withstand the relatively high temperatures required to effect proper drying of the aggregates.

A still further object of the invention is to provide apparatus of this character that will require a minimum amount of servicing and repair.

Another object of the invention is to provide apparatus of this character that is simple in construction and reliable in operation.

It is still another object of the invention to provide mechanism of this character that is relatively inexpensive to manufacture.

The characteristics and advantages of the invention are further sufficiently referred to in connection with the following detailed description of the accompanying drawings Which represent one embodiment. After considering this example, skilled persons will understand that Variations may be made without departing from the principles disclosed, and I contemplate the employment of any structures, arrangements or modes of operation that are properly within the scope of the appended claims.

Referring to the drawings:

FIG. l is a side view of drying apparatus embodying the present invention with a portion broken away to show the interior construction;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is an enlarged fragmentary view of the leading side of a lifter;

FIG. 4 is a fragmentary view of the opposite side of the lifter; and

FIG. 5 is an enlarged sectional view taken on line 5-5 of FIG 3.

Referring more particularly to the drawings, there is shown a kiln comprising cylindrical shell arranged substantially horizontally but with the inlet end 11 higher than the outlet end 12. The shell llt) is provided with a plurality of rings 14 which are secured concentrically on the exterior of said shell and which are spaced apart longitudinally thereof. The rings 14 are secured to the shell by any suitable well known means such as Welding, bolts or the like and are operably disposed on rollers 15 rotatably mounted on support means 17 attached to longitudinally extending laterally spaced members or beams 18 of a supporting frame, indicated generally at 19, which rest on a supporting surface such as a floor, foundation, or the like. A gear ring 20 is secured on the exterior of the shell 10 and is connected to a driving sprocket 21 by means of a chain 22. Sprocket 21 is attached to a drive shaft 23, the front end of such shaft 23 being operably disposed in a bearing 24 secured to the frame member 18 while the opposite end of said shaft is operably mounted in a bearing 25. Shaft 23 is driven by any suitable means such as an electric motor 26 which is connected to said shaft 23 by means of a belt drive 27 mounted on pulleys 2S and 29 on the motor shaft 30 and the adjacent end of the shaft 23 respectively.

Material to be heated and dried by the apparatus is delivered to the inlet end 11 of the shell 10 by any suitable means shown as comprising a chute 35 which projects into the inlet end of said shell 10 in the well kno-wn manner.

The device is of the counterow type wherein the ire is directed into the shell from the discharge end so that the hot combustion gases from the fire flow in the direction opposite the direction of movement of the aggregate delivered into the inlet end of said shell.

Within the shell are a plurality of longitudinally extending, annularly spaced lifters, indicated generally at 40. These lifters may be of various designs but are shown herein as being channels, that is, said lifters are in the shape of a wide, shallow U in cross-section, there being a radially extending bottom portion 41 connecting the outer and inner sides or

walls

42 and 43 respectively, which are normal to said bottom portion 41. The outer wall 42 of each lifter is secured to the inner side of the shell 10 by means of welding, bolts, or other suitable means, and at the back of said lifters are angle irons or members 44 which are also secured to the inner side of the shell and back side of the respective lifters by welding or other suitable means, said members 44 serving to strengthen said lifters 40. The inner side Walls 43 extend in the same direction as the side walls 42 and both extend from the side edges of the bottom 41 in the direction of rotation of the shell. Inasmuch as the lifters 40 are all of the same construction, a description of one only need be given. Each lifter has a series of openings or slots 46 adjacent the inner -wall 43, said slots being formed by cutting out tongues 47 and bending same outwardly from the back side of the wall 41 of the `lifter from the bottom of 4l. The tongues 47 are inclined from the normal along the edge 48 relative to the adjacent side wall 43, said tongues having outer free edges 49 which are substantially parallel to the wall 43. Each tongue 47 has a free edge 50 which extends from one end of the edge 49 inwardly relative to the lifter and terminates at the `forward end of the edge 48 of the tongue which joins the bottom wall 41. At the opposite end of the edge 49 there is a longitudinally extending free edge 51 which is inclined inwardly and which terminates in a free end portion 52 at the inner end of the tongue. The openings 46 thus provided are largest adjacent the wall 43 so that said openings are in the nature of slots which are small enough to prevent larger rock of the aggregate from passing throught while at the same time are large enough to allow sand and fine rock dust to pass therethrough.

As viewed in FIG. 2, the shell 10 rotates counterclockwise. The lifters 40 pick up the aggregate at the bottom of the shell and carry same upwardly as the shell rotates, aggregate material being dropped from said lifters when the angle of repose of the material contained therein is such that said material will fall off. This falling off action, once it starts, becomes continuous and develops aggregate curtains.

As the shell rotates, the lifters rise arcuately and when the aggregate on each lifter reaches said angle of repose the sand, which is trapped behind the Wall 43 thereof, begins to fall through the slots 46. It will be noted that the sand falls rather quickly, sifting through the rocks and reaching the slots and sifting through same before any of the rocks have fallen from the lifter. As the lifter rises higher and the angle thereof becomes steeper, most of the sand has filtered through the slots along the side of the shell interior. Thus the rock material, when it begins to flow olf the lifter, is cascaded out beyond 4the sand and because the sand has been removed from the gangue, the rock receives the full blast of the tire out of the presence of the stealer of heat, said rock being completely uninsulated in any way by the sand and fines within the composite gangue at this interval of heat application.

It is thought that the invention and many of its attendant advantages Will be understood from the foregoing description and it is thought that it will be apparent that various changes may be made in the form, construction and arrangement of parts of the invention without departing from the spirit and scope thereof or sacrificing all of its material advantages.

I claim:

1. Apparatus for drying various aggregates used in the paving industry and the like, comprising: a cylindrical shell having an inlet at one end and an outlet at the other end, the outlet end of said shell being lower than the inlet end; means for rotatably supporting said shell; means operably connected to said shell for effecting rotation thereof; means for supplying a composite aggregate material to the inlet end of said shell, the outlet end of said shell being adapted to have hot gases discharged thereinto; a plurality of longitudinally extending, annularly spaced lifters secured to the interior of said shell, each of said lifters including a bottom wall having one side secured to the shell and extending radially of said shell; an inner side wall extending longitudinally of the inner edge of said bottom wall and substantially normal thereto, the free edge of said inner wall facing the direction of rotation of said shell; and a plurality of elongated tongues, spaced apart longitudinally relative to the lifter, said tongues being cut from said bottom wall with one side of said tongues connected to said bottom wall, said tongues being bent outwardly of the bottom wall to provide respective openings adjacent said inner wall of the lifter, said tongues being spaced their greatest distance outwardly of the bottom wall adjacent said inner wall so that each of said openings has its largest portion adjacent said inner wall and -being adapted to allow the finer components of the aggregate material to pass therethrough while preventing the larger components from passing therethrough.

2. Apparatus for drying various aggregates used in the paving industry and the like, comprising: a cylindrical shell having an inlet at one end and an outlet at the other end, the outlet end of said shell being lower than the inlet end; means for rotatably supporting said shell; means operably connected to said shell for effecting rotation thereof; means for supplying a composite aggregate material to the inlet end of said shell; a plurality of longitudinally extending, annularly spaced lifters for said shell, each of said lifters including a 'bottom wall secured at one side to the interior of said shell and extending radially from said shell, an inner side wall extending longitudinally at the inner edge of said bottom Wall and substantially normal thereto, the free edge of said inner wall facing the direction of rotation of said shell, and a plurality of elongated tongues, spaced apart longitudinally relative to the lifter, and cut from said bottom wall with one side connected thereto, said tongues being bent outwardly of the bottom wall to provide respective openings only adjacent said inner Wall of the lifter, through which only the finer components of the aggregate may pass.

3. A lifter for a counterflow aggregate drier, comprising: an elongated bottom wall; anges along the side edges of said bottom wall and extending normally in the same direction from the plane of said bottom Wall; and a plurality of elongated tongues, spaced apart longitudinally relative to the lifter and extending at an acute angle relative to one of said ilanges, said tongues being cut from said bottom wall with one side of said tongue connected to said bottom wall, said tongues being bent outwardly of the bottom wall to provide respective openings only adjacent said one ange, each of said openings having a largest portion thereof adjacent said ilange and being adapted to allow the iiner components of aggregate material to pass therethrough while preventing the larger components from passing therethrough.

4. In a lifter for aggregate driers: a -bottom wall; a flange at one side of said bottom Wall; and a plurality of elongated tongues, cut from said bottom wall with one side of said tongue connected to said bottom wall, said tongues being bent outwardlly of the bottom wall to provide respective openings only adjacent said flange, each of said openings having a largest portion thereof adjacent said flange and being adapted to allow iner components only of the aggregate material to pass therethrough.

5. In apparatus for drying Various aggregate used in the paving industry and the like: a rotatable cylindrical shell lhaving an inlet at one end and an outlet at the other end, the outlet end of said shell being lower than the inlet end; and a plurality of annularly spaced lifters secured to the interior of said shell, each of said lifters including a bottom wall extending substantially radially inwardly of the shell Wall, an inner wall extending ahead of said bottom Wall in the direction of rotation and substantially normal thereto, said bottom wall having openings only adjacent the inner wall of the lifter spaced apart longitudinally of said inner Wall, through which the ne components of the aggregate may pass, and a tongue extending from said bottom wall over each of said openings at the side of the bottom wall opposite said inner wall, the portions of the bottom wall inwardly of the openings adjacent said inner wall of the lifter being imperforate.

6. A lifter for an aggregate drier, comprising: an elongated bottom wall adapted to be secured along one edge to the interior of a drier shell; a flange extending longitudinally of the bottom wall `at an angle substantially normal thereto and in spaced relationship to said edge, said bottom wall having a plurality of elongated openings arranged at an angle relative to the plane of said flange and `adjacent thereto only at the side thereof adjacent said edge of the bottom wall, and a tongue extending from said bottom wall over each of said openings at the side of the bottom Wall opposite said flange.

7. In apparatus for drying aggregate used in the paving industry and the like: a rotatable cylindrical shell having an inlet at one end and an outlet at the other, the outlet end of said shell being lower than the inlet end; and a plurality of annularly spaced lifters secured along the outer edges to the interior of said shell, each of said lifters including a bottom wall in a plane substantially radial with respect to the shell and of a width substantially less than the radius of the shell; a flange extending longitudinally from said bottom wall in spaced relation to the shell wall, said flange being at an angle substantially normal to said bottom wall, the latter having a plurality `of elongated openings therethrough only adjacent the flange and at an obtuse angle relative to the plane of the ange and a tongue extending from said bottom wall over each of said openings at the side of the bottom wall opposite said inner Wall.

8. In apparatus for drying various aggregate used in the paving industry and the like; a rotatable cylindrical shell having an inlet at one end and an outlet at the other end, the outlet end of said shell being lower than the inlet end; a plurality of annularly spaced lifters secured to the interior of said shell, each of said lifters including a bottom wall extending inwardly of the shell wall; an inner wall extending ahead of said bottom wall in the direction of rotation, said bottom wall having openings only adjacent said inner Wall of the lifter spaced apart longitudinally of said inner wall through which the -finer components of theaggregate may pass; and a tongue extending rfrom said bottom wall over each of said openings at the side of the bottom wall opposite said inner wall, the portion of the bottom wall inwardly of the openings adjacent said inner wall of the lifter being imperforate.

References Cited in the le of this patent UNITED STATES PATENTS 1,046,664 Smith Dec. l0, 1912 1,079,153 Topf Nov. 18, 1913 2,595,509 Brown May 6, 1952 2,709,306 Magnusson et al May 31, 1955 FOREIGN PATENTS 330,624 France Aug. 22, 19,03