US2411751A - Drier for aggregates and the like - Google Patents

Description

Nov. 26, 1946 J. 'OVE'RMAN 2,411,751

-DRIER FOR AGGREGATES AND THE LIKE Filed July 1 1943 INVENTOR.

if the aggregate was quite I gases, etc., discharge from supports feed screw 13 carried by shaft Patented Nov. 26, 1946 UNITED STATES PATENT OFFICE 2,411,751 DRIER FOR AGGREGATES AND THE LIKE Ivan J. Overman, Marion, Ind. Application July 1, 1943, Serial No. 492,984

18 Claims. 1

This invention relates to driers for aggregates and the like.

. drier illustrated, described and claimed in Patent No. 2,290,765, dated July 21, 1942. In actual use of this patented structure two serious operating objections were discovered. The first was, moist, the resulting drying stage did not have free back and interfered with the second drying stage. The second was more serious and potentially dangerous. The resulting back pressure, as it were, frequently quenched one of the flames. The combustible mixture then accumulated in the drier until it accidentallyignited from the other flame. explosion of detonating andpotentially devastating character.

The chief object of the present invention is vapor in the intial escape but worked I to insure proper drying in bothstages andmore particularly to insure that one flame will always ignite the combustible mixture from the unlit torch before such mixture can accumulate in the drier to such a degree as to be dangerous. I

The chief feature of the present invention consists in first stage ventingand inclusion of ignition tubes in the drier. c

.Other objects and features of the present invention will be set forth more fully hereinafter.

The full nature of the invention will be understood from the accompanying drawing. and the 7 following specification and claims:

In the drawing Fig. l is side elevation of a drier embodying the invention, the outer housing such as illustrated in said patent, if used, being omitted.

Fig. 2 is an elevational View of the aggregate supply and discharge end of the drier, the housing being omitted.

In the present form of the invention, like the aforesaid patent, the aggregate is supplied to and discharged from the same end of the drier. Differing from said patent, the moisture, burned the end opposite that last mentioned. This has certain operational advantages.

Herein It indicates framework that may be casedto form a housing as aforesaid. It also the hopper ll leading to stationary supply passage l2 in which is mounted aggregate l4 rotatable by suitable means not shown. 7

The screw feeds the aggregate in a regulated manner and degree into the rotatable drum structure and into the inner drum thereof. This The result was an inner drum has a tapered intake throat portion 15. The end wall I6 of the drum structure is stationary. The discharge end of tube l2 projects into the central aperture in the end l6 defined by collar lea and into the intake end l5 as illustrated.

The inner drum includes a main frusto-conical body portion 11, which is a continuation of intake portion l5. An outer cylindrical drum l8 envelopes the inner drum and its right hand end, see Fig. 1, has a close fit with rim l6b of closure I6. Annular rings 19 and 28 are carried by the inner and outer drums interiorly and exteriorly, respectively, and suitably connected together by bolts, etc., 2|. In this manner the inner drum is supported within and by the outer drum with a channel therebetween.

Within the inner drum and secured to the interior thereof and co-extensive with portion I1 thereof are the annularly spaced flights or vanes 22. These are pitched about 15 and six are utilized. These flights are spaced apart to somewhat delay aggregate travel so that aggregate travels longitudinally, both interiorly and exteriorly, notwithstanding the difference in drum diameters, and is substantially atequal rates and equal to the feeding rate of screw l3.

Secured to the interior of the exterior drum I8 are four flights of annularly spaced vanes 23, there being six in each flight and each pitched about Drum rotation is in the direction of the arrow, see Fig. 2, and. the speed is about 10 R. P. M.

The exterior of drum I8 is provided with the bearing bands 24 and these in general are substantially as illustrated in Figs. 1 and 2 of said patent and as so illustrated one set of rollers 25 herein is smooth and the other set 26 is grooved. The power for shafts H is omitted for clearness.

The intake end of the drum structure has its stationary end It apertured at 21, which aperture is the aggregate outlet of the drum structure. End I6 is also apertured at 28 positioned a slightly to the left of the centralplane in Fig. 2.

3 directed shield 35 providing a large central opening. Carried by the frame I is a stationary plate 36, apertured at 3'! and having an inwardly and downwardly directed deflector 39 at its upper edge which is slightly above the drum axis of rotation.

A similar burner 45!, ported at M and having nozzle &2 connected to a source of air pressure by line 43 and a source of oil or gas under pressure by line id including valve 45, directs its flame through opening 31 and into the inner drum near the bottom thereof.

The aggregate is supplied in regulated amount and continuously by screw l3 from hopper H to the inner drum at the intake end. It is rotated by the blades 22 in drum rotation and i gradually worked to the left hand end'of same, thus discharging to the other drum. Any aggregate discharged outwardly and from the inner drum engages deflector 39 and is returned to the outer drum. Any aggregate that falls down at this end and from the outer drum is also so returned by the baifie. The outer drum vanes, in drum rotation, work the aggregate back to the supply end until it is discharged through outlet 27.

Burner 48 also is oif-center and to a greater degree than burner 29 and is at a higher elevation than the latter. The flame from burner 48 passes into the inner drum and passes toward the aggregate intake end thereof. Moisture in the aggregate is vaporized and rises in the drum with the hot products of combustion. The screw feed blocks escape from closure it, so the aforesaid rises and returns and finally passes out through the central aperture in ring flange 35 and above plate at and deflector 39.

The flame from burner 29, entering at 23, passes along the drum structure in the annular channel betweenthe inner and outer drums and finally discharges inwardly at the plate 35 and similarly escapes from the drum structure. The housing, not shown, may include a stack to facilitate such discharge.

The foregoing arrangement, accordingly, prevents the development of moisture excessive back pressure in the drum, since substantially no restrictions are included preventing, or materially retarding continuous flow and escape of vaporized moisture and products of combustion through and from the drum structure.

Reference will'again be had to Fig. 1 wherein there is illustrated a plurality of tubes ed, open at opposite ends and projecting through the intake end of the inner drum substantially at the junction between portions i and I1 thereof. These tubes, of which two are herein illustrated at 180, have their lesser divergent ends closest to burner 40 and positioned so that said ends successively register therewith. The greater divergent ends of said tubes are closest to burner 2 and positioned so that said ends successively register therewith.

Thus there is always restricted communication between'the inner drum chamber and the outer annular channel. Furthermore, in drum rotation, at least every three seconds R. P. M. times 2), a tube is aligned, as it were, between nozzles 29 and 48. Now if the burner flame, accidentally or intentionally, goes out for either burner, the flame from the other burner will ignite the unlighted combustible mixture, and

before a dangerous concentration thereof builds up in the drum. Accordingly, danger of destructive explosions is completely eliminated. These two tubes also provide a pressure equalizing ari 2, hot gases will escape about said tube and heat same and thus preheat the aggregate in the worm tube creating a vapor pressure therein to seal, as it were, the inner drum at the intake end. This accounts for the interior of the inner drum being at a higher temperature than the outer annular chamber.

While the invention has been illustrated and described in great detail in the drawing and foregoing description, the same is to be considered as illustrative and not restrictive in character.

The several modifications described herein as well as others which will readily suggest themselves to persons skilled in this art, all are considered to be Within the broad scope of the invention, reference being had to the appended claims.

The invention claimed is:

1. An aggregate'drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to flame the interior of the outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the adjacent end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming the interior of the inner drum through the last mentioned aperture.

2. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which of the adjacent end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming the interior of the inner drum through the last men- "tioned aperture, and wherein the inwardly directed burners are at difierent elevations and oifset laterally of the drum structure Vertical central plane.

3. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drumstructurehaving apertur'es "through which aggregate-is supplied to 'the'inner' drum, "and aggregate is discharged from the outer drum, a burner arranged to flame the interior of the outer drum'and through --a closure 'aperturetherein,"'a' stationary partial closure at 'theopposite end of the drum" structure, the central inner "drum chamber and included outer -annular chamber venting therefrom above the latter closure; the inner "drum at the-said opposite end of the structure terminating" short of the-adjacent end of the-outer'drumfor-aggre gate transfer, said latterclosure 'having'anaper ture-therein, and a second burner flaming-the interior ofthe innerdrum-through the" last mentioned aperture,- and wherein the inwardly -di rected burners are at different elevations. and offset laterally of the drum structure vertical central plane andinwardlydirected-flange means on the end of the outer drum -opposite the intake end of the 'drum' structure and' spaced longitudinally of the'adja'cent end-of the inner drum and having aminner edge that-is at a greater radial distance from the drum rotation axis than the burner adjacentthat end of drum structure --is spaced from the aforesaid axis for non-interfer- 1 ing flaming by the last mentioned burner of the 'drumstructure central chamber and aggregate transfer from the inner to -the-outer drum.

4; "An aggregate drier comprising in combinationa rotatable drum "structure including "an -i-nner drum and "anouter drumthrough which aggregatepasses in succession, a stationary closure for one -end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer-drum, a burner arranged to flame the interior of the outer *drum and through'a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, the central innen drum chamber and included outer annular chamber venting therefrom above the latterclosure, the-inner" drum at the said -opp'os-ite end *of the structure terminating short oftheadjacent endof the'outer drum for aggregate transfensaid latter closure having an aperturetherein; anda secondburner flaming the interior of the inner drum through the last -mentioned aperture, and wherein the inwardly directed burners are at different elevationsand "offset laterallyof the drum structure vertical central plane and inwardly directed flange means on the end'of the-outer drumopposite the intake end'of the drum structure, and spaced longitudinally of the adjacent end of the innerdrum and having an inner edge that is at a greater radial distance from the drum rotation axis than the '-burner "adjacent that end of drum'structure is spaced from the aforesaid axis for non-interier-ing flaming by the last mentioned burner of the drum structure central {chamber and aggregate transfer from the inner to the outerdrum,

the secondmentioned partial closure at its upper edge having an inwardly 'and downwardly directed deflector 'forthepurpose set forth and terminating at its lower inner edge above the flame path from said last mentioned burner.

/ 5. An aggregate drier comprising incombination a rotatable drum structure'including an inner-drum and an outer drum through which aggregate passes in succession, a-stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, -a burner arranged to flame the "interior of the outerdrum and-through a- -clo-" ture, and wherein the inner drum is of tapering mentioned aperture, and wherein the inner drum is of tapering type with its smallest end constituting the aggregate intake of the structure, andprotector tube means extending angularly through the inner drum adjacent the intake en'd'thereof, the end of said tube means closest to the intake end of the structure being at a,

greater distance from the structure axis of rotation than the opposite end of the said tube means. 7 I

6-. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, aburner arranged to flame the interim" of the outer drum and through a closure aperture therein, a stationary partial closure at -the opposite-end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closurethe inner drum at the said opposite end of the structure terminating short of the adjace'nt end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming the interior of the inner drum through the last mentioned aper ture," and wherein the inner drum is of tapering "type with its smallest end constituting the aggregate'intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end P of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at different elevations, the intake endburner being at a greater distance from the structure axis of ro- "tation.

7. An aggregate drier comprising incombination a rotatable drum structure includingan inner drum and an outer drum through which ag- 'gregate passes insuccession, a stationary closure for one end of said drum structure having aperture's' through which aggregat is supplied to the inner drum, and aggregate is'discharged from the outer drum, a=burner arranged to flame the interior ofthe outer drum and through a closure "aperture therein, a stationary partial closure at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the adjacent end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming the interior of type with its smallest end constituting, the aggregate intake of the structure, and protector tube 'mea n's extending angularly through the "inner drum adjacent the intake'end thereofg'the amen end of said tube, means closestto the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at difierent elevations, the intake end burner being at a greater distance from the structure axis of rotation, the inner drum end of the tube means being distant from said axis substantially the distance from the same that the second mentioned burner is therefrom.

8. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum-structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to flame the interior of the outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of th structure terminating short of the adjacent end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming the interior of the inner drum through the last mentioned aperture, and wherein the inner drum is of tapering type with its smallest end constituting the aggregate intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at different elevations, the intake end burner being at a greater distance from the structure axis of rotation, the outer drum end of the tube means being distant from the said axis slightly less than the distance from the same that th first mentioned burner is therefrom.

9. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to flame the interior of th outer drum and through a closure aperture therein, a stationary partial closure at th opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the adjacent end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming the interior of the inner drum through the last mentioned aperture, and wherein the inner drum is of tapering type with its smallest end constituting the aggregate intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at different elevations, the intake end burner being at a greater distance from the structure axis of rotation, the inner drum end of-the tube means being distant from said axis substantially the distance iruni'tne same that the second mentioned Dulllbl'islentil-U111, tne outer ul-uin end 01 the tune means being distant iroill the said axis slightly less than the distance lronl tne same that the met mentioned burner is tnei'eirom.

1.0. ml aggregat urler comprising in combination a rotatable uruin structure including an inner drum and an outer urum through which aggregate passes in succession, a stationary closure ror one end of said drum structure having apertures through which aggregate is su plied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to name tne interior of tile outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of tne orum structure, the central inner drum chamber and included outer annular chamber venting therelrom above the latter closure, the inner drum at the said opposite end of the structure terminating short or the ad acent end of the outer drum ior aggregate transfer, said latter closure having an aperture therein, and a second burner naming the interior of the inner drum through the last mentioned-aperture, and wherein tne inner drum is of tapering type with its smallest end constituting the aggregate intake or tne structure, and protector tube means extending angularly through the inner drum adJacent the intake end thereof, th end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the

burners being at different elevations, the intake end burner being at a greater distance from the structure axis of rotation, both burners being ofiset laterally of the central vertical plane of the drum structure.

11. Anaggregate drier comprising in combination a rotatable drum-structureincluding an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum'structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to flame the interior of the outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the adjacent end of theouter drum for aggregate transfer, said latter closure havingan aperture-therein, and a second burner flaming the interior of the inner drum through the last mentioned aperture, and wherein the,inner drum is of tapering type with its smallest end constituting the aggregate intak of the structure, and protector tube means extending angularly through the inner drum-adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at different elevations, the intake end burner being at a greater distance from the structure axis of rotation, both burners being offset laterally of the central vertical plane of the drum structure, the intake end burner being laterally offset to a lesser degree.

' 12. An aggregate drier comprising in combination a rotatable drum structure including an inner urumrand-an outer drumthrough which aggregate passes in succession, a stationary closure for one end. of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate isdischarged from the outer drum, a burner arranged to flame theinterior f the :outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drumv structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the adjacent end of the outer drum for aggregate trans fer, said latter'closure having an aperture there- .in, and a second burner flaming the interior of the inner drum through the last mentioned aperture, and wherein the inner drum is of tapering typewith its smallest end constituting the aggregate intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at different elevations, the intake end burnerbeing at a greater distance from the structure axis of rotation, both burners being offset laterally of the central vertical plane of the drum structure, the inner drum end of the tube means being distant from said axis substantially the distance from thesame that the second mentioned burner is therefrom.

13. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and .an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum a burner arranged to flame the interior of the outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the adjacent end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming the interior of the inner drum through the last mentioned aperture, and wherein the inner drum is of tapering type with its smallest end constituting the aggregate intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at different elevations, the intake end burner being at a greater distance from the structure axis of rotation, both burners being offset laterally of the central vertical plane of the drum structure, the outer drum end of the tube means being distant from the said axis slightly less than the distance from the same that the first mentioned burner is therefrom;

14. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer :dru'm, a burner arranged to flame the'interior of the outer drum and through a closure aperture therein, a stationary partial closur at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the adjace-ntend of the outer drum for aggregate transfer, said latter closure having an aperture therein,;and a second burner flaming the interior of the;im'ierdrum through the last mentioned aperture, and wherein the inner drum is of tapering type with its smallest end constituting the aggregate intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end of sai'dtube means closest to the intake end 'of the structure being at a greater distance from th structure axis of rotation than the opposite end of the said tube means, the burners being at different elevations, the intake end burner being at a greater distance :rrom the structure axis of rotation, both burners being offset laterally of the central. vertical plane of the drum structure. the inner drum end of the tube means being distant from said axis substantially the distance from the same that the second mentioned burner is therefrom, the outer drum end of the tube means being distant from the said axis slightly less than the distance from the same that the first mentioned burner is therefrom.

'15. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and'an outer drumthrough which 'a'ggregate passes succession, a stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to flame the interior of the outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, th central inner drum chamber and included 'outerannular chamber venting therefrom above the latter 'clo'sure, the inner drum at the said opposite end of the structure terminating short of the adjacent end of the outer drum for aggre ate trans "fer, said latter closure having an aperture therein, and a second burner flaming the interior of the inner drum through the last mentioned aperture, and wherein the inner drum is of tapering type with itssmallest end constituting the aggregate intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at different elevations, the intake end burner being at a greater distance from the structure axis of rotation, both burners being offset laterally of the central vertical plane of the drum structure, the intake end burner being laterally offset to a lesser degree, the inner drum end of the tube means being distant from said axis substantially the distance from the same that the second mentioned burner is therefrom.

16. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate' passes in succession, a stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to flame the interior of the outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the ad- 'acent end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming the interior of the inner drum through the last mentioned aperture, and wherein the inner drum is of tapering type with its smallest end constituting the aggregate intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means, the burners being at difierent elevations, the intake end burner being at a greater distance from the structure axis of rotation, both burners being offset laterally of the central vertical plane of the drum structure, the intake end burner being laterally offset to a lesser degree, the outer drum end of the tube means being distant from the said axis slightly less than the distance from the same that the first mentioned burner is therefrom.

17. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum structure having apertures through which aggregate is supplied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to flame the interior of the outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, the inner drum at the said opposite end of the structure terminating short of the adjacent end of the outer drum for aggregate transfer, aid latter closure having an aperture therein, and a second burner flaming the interior of the inner drumthrough the last mentioned aperture, and wherein the inner drum is of tapering type with its smallest end constituting the aggregate intake of the structure, and protector tube means extending angularly through the inner drum adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from 1e structure axis of rotation tnan the opposite end of the said tube means, the burners being at difierent elevations, the intake end burner being at a greater distance from the structure axis of rotation, both burners being offset laterally of the central vertical plane of the drum structure, the intake end burner being laterally offset to a lesser degree, the inner drum end of the tube means being distant from said axis substantially the distance from the same that the second mentioned burner is therefrom, the outer drum end of the tube means being distant from the said axis slightly less than the distance from the same that th first mentioned burner is therefrom.

18. An aggregate drier comprising in combination a rotatable drum structure including an inner drum and an outer drum through which aggregate passes in succession, a stationary closure for one end of said drum structure having apertures through which aggregat is supplied to the inner drum, and aggregate is discharged from the outer drum, a burner arranged to flame the interior of the outer drum and through a closure aperture therein, a stationary partial closure at the opposite end of the drum structure, the central inner drum chamber and included outer annular chamber venting therefrom above the latter closure, th inner drum at the said opposite end of the structure terminating short of the adjacent end of the outer drum for aggregate transfer, said latter closure having an aperture therein, and a second burner flaming th interior of the inner drum through the last mentioned aperture, and wherein there is provided a feed screw device for aggregate supply, the axis of which is coincident with the drum structure rotation axis, the screw device adjacent end portion of the inner drum being appreciably tapered and the remainder of the inner drum being of frusto-conical type, the opposite end of the inner drum terminating adjacent but slightly spaced from the outer drum, the latter being substantially cylindrical and longer than the-inner drum at the said opposite end thereof and wherein the inner drum is of tapering type with its smallest end constituting the aggregate intake of the structure, and protector tube means exending angularly through the inner drum adjacent the intake end thereof, the end of said tube means closest to the intake end of the structure being at a greater distance from the structure axis of rotation than the opposite end of the said tube means.

IVAN J. OVERMAN.

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