Rotary aggregate drier
United States Patent 2082970

This invention relates to a continuous rotary drier for drying and heating aggregate preparatory to mixing with asphalt, cement and the like for producing road surfacing materials. It has been the general practice to remove the water content and moisture from gravel, sand and the like and...

Overman, Ivan J.
Application Number:
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Filing Date:
Ross, Mcclain S.
Primary Class:
Other Classes:
34/137, 432/106, 432/110, 432/117
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This invention relates to a continuous rotary drier for drying and heating aggregate preparatory to mixing with asphalt, cement and the like for producing road surfacing materials.

It has been the general practice to remove the water content and moisture from gravel, sand and the like and preheat it for mixing purposes by spreading it out upon huge drying pans, applying heat thereto for removing the moisture and heating the material in batches, after which the batches are conveyed to a mixer for mixing with asphalt and other ingredients, such as cement.

The purpose of this invention Is to greatly facilitate and speed up the drying and heating operation by continuously passing the different grades of aggregate through drying tubes which continuously discharge the treated aggregate onto a conveyor which carries it to the mixer.

The principal feature of the invention resides in the angular position of the tube such that the aggregate will pass therethrough by force of gravity, being fed thereto at the upper end and discharged at the lower end, such discharge being continuous and at such speed of discharge as may be most efficient for production purposes.

Another feature of the invention resides in employing sections of the tube of different diameters, the largest section being provided at the intake end of the tube and the smallest section at the discharge end. Each of said sections is provided with baffle or retarding rings extending about the inner periphery, and longitudinal agitating ribs spaced about the inner surface of the tubular sections and extending inwardly therefrom. By means of this arrangement, the passage of the aggregate through the tube is retarded sufficiently to permit a full removal of the moisture.

By means of the agitating ribs, the particles of aggregate are separated and distributed about the tube so as to receive the full effect of the heated gases passing therethrough.

Another feature of the invention resides in discharging a flame and the resulting heated gases directly into the discharge end of the tube, whereby the flame from a burner or the like will extend substantially throughout the length of the discharge section and the aggregate is caused to pass directly through the flame for thoroughly Sbaking and bringing it to a high temperature, after being dried by the passage of hot gases therethrough, immediately before its discharge onto a conveyor belt or the like ready for mixing.

Thus, one of the principal advantages resides In the free discharge of the aggregate directly from the end of the tube into which the flame is directed.

The full nature of the invention will be understood from the accompanying drawing and the following description and claim: Fig. 1 is a side elevation of the tube mounted in operative position. Fig. 2 is a section taken on the line 2-2 of Fig. 1. Fig. 3 is a section taken on the line 3-3 of Fig. 1. Fig. 4 is a section taken on the line 4-4 of Fig 1. Fig. 5 is a diagrammatic illustration of a battery of tubes associated with the conveyor and mixer.

In the drawing, there is shown a drying tube comprising an upper enlarged section 10 for receiving aggregate, such as sand, gravel or the like, an intermediate reduced section II and a still smaller discharge section 12. The tube is supported for rapid rotation at an angle to the horizontal with the section 10 elevated substantially above section 12. For this purpose, section 10 is provided with a peripheral track ring 13 which rides upon a plurality of flanged wheels 14 mounted upon a bracket 15 which in turn is supported upon a trestle 16. The discharge section 12 is likewise provided with a track ring 17 about the periphery thereof which is supported for rotation upon a plurality of flanged rollers 18 mounted upon a bracket 19 supported by a trestle 20. The trestle 20 supports a driving motor 21 which drives the tube through the medium of a peripheral sprocket 22 and chain 23.

Any suitable means may be provided for feeding the aggregate into the upper open mouth of the tubular section 10, there being herein illustrated a conveyor chain 24 having buckets 25 adapted to receive the aggregate 26 carried in a hopper 27, the buckets 25 dumping the aggregate carried from the hopper into-the upper end of the tube. The chain 24 is driven by a sprocket 28 from a motor 29 supported upon standards 30. At the lower or discharge end of the section 12, a suitable heating device 31 is provided, preferably in the form of a distillate torch burner which is suspended from a suitable overhead structure by a rod 32, the air and gas being delivered thereto from the usual sources of supply through the pipes 33. The distillate torch Is so supported as to direct the flame discharged therefrom directly into the discharge end of the section 12 and upwardly therethrough. For retarding the passage of aggregate through the various sections of the tube, section 10 is provided interiorly with a plurality of rings 34 which form inwardly extending retarding flanges which cause the aggregate to temporarily pile up behind them and overflow through their central apertures. In a similar manner, section II is provided with a plurality of such retarding rings 38 of less depth, and section 12 is similarily provided with such rings 36 of still less depth. Extending longitudinally of each section and intermediate the respective retarding rings, there are a plurality of peripherally spaced and radially positioned agitating ribs, the ribs 37 extending through section 10 being of the same width as the closed portion of the rings 34, while the ribs 38 of section II are the same width as the closed portion of the rings 35, likewise the ribs 39 of section 12 are the same width as the closed portion of the rings 36.

In operation, aggregate is constantly fed by the chain 24 from the hopper into the upper end of the tube or section 10. Inasmuch as the tube is rapidly rotating, the aggregate will build up behind the first ring 34 between the ribs 37. However, the rotation of the tube is not sufficient to retain the aggregate about its periphery by centrifugal force, so that as the aggregate is carried about the tube by its rotation, it will drop from the upper to the lower portion thereof, causing separation and agitation of the particles as well as temporary retarding thereof. Thus, the aggregate will pass step by step from one ring to the other with constant agitation and passage through the center of the tube as it is spilled over from top to bottom. During such passage of the aggregate through the several sections, the hot gases from the burner at the lower end will pass upwardly through the central opening of the rings, but will be baffled and retarded by the rings in its passage and thoroughly agitated by the ribs. As a result, the full heating effect of the hot gases will be applied to all surfaces of the particles of aggregate so that the gases will carry the moisture therefrom and effect a thorough drying. As the aggregate reaches the discharge section 12, it enters a combustion chamber, and, by reason of the agitating action of the ribs and the retarding action of the rings, it will be caused to repeatedly pass directly through the flame introduced into the lower end of the tube. Inasmuch as the aggregate has been previously dried, it will thereupon be thoroughly baked to a high degree so that as it discharges from the tube, it will have a red glow and be of such temperature as to maintain suffcient heat until it is carried on the conveyor to the mixing chamber.

It has been found that mud resulting from the1 drying operation accumulates at about the center of section I so that it is desirable to provide a manhole 40 in the side of the tube at that point through which access may be had to section II for periodically removing the accumulation of mud therefrom when the drier is shut down.

As diagrammatically illustrated in Fg. 6, there is shown a battery of tubes as above described indicated at A, B and C. For purposes of illustration, it may be assumed that tube A dries and discharges at high temperature No. 9 stone.

B may dry, heat and discharge coarse sand, while tube C may dry, heat and discharge fine sand. The discharge from the respective tubes is received by the conveyor belt D. At one position on the belt, a conveyor E may carry cement thereto, whereupon the combined highly heated aggregate of No. 9 stone, coarse and fine sand and cement may be discharged into the hopper F leading to the usual mixing chamber.

The invention claimed is: An apparatus for drying and heating aggregate including an elongated tube, means for supporting said tube at an angle to permit the aggregate to slide therethrough by gravity, means for feeding aggregate into the upper end of said 3 tube, the lower end thereof being of reduced diameter to provide a discharge nozzle for the aggregate, means for rapidly rotating said tube, and a burner having its mouth projected into said nozzle for injecting a flame therein, the axis of the burner being inclined downwardly with respect to the axis of said nozzle and the diameter of said discharge nozzle in relation to the flame injected therein being such as to cause the aggregate to pass directly through said flame before being discharged from said nozzle. IVAN J. OVERMAN.