Granular product blending and cooling rotary drum

A rotary drum configuration for the efficient blending, cooling, and screening of granular products having an outer cylindrical shell, an intake end, and a discharge end. The rotary drum is normally rotated at a predetermined speed by means of a conventional drive package. Disposed on an inner surface of the cylindrical shell are a plurality of compound helical flights and scoops, configured to blend granular product as it cascades from the intake end to the discharge end of the rotary drum. A coaxially disposed cylindrical air passage adjacent the discharge end of the rotary drum directs a counter flow of cooling air through the rotary drum towards the intake end, cooling the cascading granular product as it approaches the discharge end, and plurality of discharge ports and grading screens in the surface of the outer cylindrical shell adjacent the discharge end provide a entrance for a second counter flow of cooling air while simultaneously providing passage for the granular product to drop downwards towards a outer coaxial discharge passage.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

The present invention relates generally to a rotary drum as used in the granular product drying field, and having a major application for the treatment of heated and moist granular products such as mold sands, grains, and fertilizers as to achieve the reclaiming, cooling, and blending of the mold granular product and in particular, to a dust collection hood and discharge chute configured to convey multiple air streams through the rotary drum for the cooling of the granular product.

There are a variety of prior patents that have been obtained upon various styles of rotary drums for use in the metal casting industry. For example, one of the early embodiments is that which is shown in U.S. Pat. No. 3,998,262 to Charles J. Didion, showing a casting shakeout unit and method of operation. Essentially, such a drum is arranged upon its structural support and rotated by means of a drive unit, so that when castings clogged with mold sand as obtained directly from the site of their casting, are then passed through the rotary drum, the mold sand is effectively separated and removed from the prepared castings, to achieve the required separation without necessitating the employment of any manual labor to attain such results.

The usage of shrouds or hoods around the discharge end of the rotary drum has been employed in the prior art, as can be seen in U.S. Pat. No. 4,050,635 to Mueller, et al., wherein the shown housing incorporated an outlet chute, at is lower end, for attaining the discharge of the castings, or its sand, therefrom, during operations of the shown device. In addition, such hoods have been used for collection and removal of sand particles, to facilitate the collection of the sand in preparation for its re-usage.

Similarly, the usage of a ventilating hood on a rotary drum, having various ventilating ports designed therein so as to accommodate the flow of air around and through the discharge end of the rotary drum, for the removal of heat from sand and containment of fines and dust, while likewise diverting the separated mold sand for passage to a discharge opening, as arranged at the bottom of the ventilating hood is shown in U.S. Pat. No. 4,981,581 to Charles J. Didion.

However, it has been found that the removal of heat from hot granular products by exposure to an airflow only at the discharge end is insufficient to reduce the temperature of the granular products to near ambient temperatures. Accordingly, there is a need for a reclaiming rotary drum configuration which is capable of removing heat and moisture from granular products from the point of intake through the discharge end, to increase the heat removal, and to reduce the granular product temperature to near ambient conditions at the discharge end.

BRIEF SUMMARY OF THE INVENTION

Briefly stated, the invention sets forth a rotary drum configuration for the efficient blending, cooling, and screening of granular products. The rotary drum is of the type that is an elongated structure, generally having an outer cylindrical shell, an intake end, and a discharge end. The rotary drum is normally rotated at a predetermined speed by means of a conventional drive package. Disposed on an inner surface of the cylindrical shell are a plurality of compound helical flights and scoops, configured to blend granular product as it cascades from the intake end to the discharge end of the rotary drum. A coaxially disposed cylindrical air passage adjacent the discharge end of the rotary drum directs a counter flow of cooling air through the rotary drum towards the intake end, cooling the cascading granular product as it approaches the discharge end. A plurality of discharge ports and grading screens in the surface of the outer cylindrical shell adjacent the discharge end provide a entrance for a second counter flow of cooling air while simultaneously providing passage for the granular product to drop downwards towards a outer coaxial discharge passage. A series of external helical flights on the outer surface of the cylindrical shell urge granular product in the outer coaxial discharge passage out the discharge end of the rotary drum. The upper section of the discharge end contains an opening therethrough, and mounted in proximity with the opening, or in communication through duct work with the opening, is a vacuum pump which is designed to provide a reduced pressure for attracting air, particularly that air in which the dust and sand fines from the granular product are entrained, so as to achieve their removal.

In an alternative embodiment of the present invention, an air manifold and air pump is operatively coupled to either the cylindrical air passage, the discharge ports, or both to provide a positive pressure counter flow of air through the respective passage or ports.

The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.

Turning toFIG. 1, a rotary drum of the present invention for effecting the blending and cooling of granular product is shown generally at10. The rotary media drum10comprises a cylindrical drum body12, which is includes a plurality of spaced circumferential drum assembly tires14disposed on an external surface16. The circumferential drum assembly tires support the rotary drum10on a conventional base (not shown). Correspondingly, a circumferential sprocket18on the external surface16engages a conventional drive mechanism (not shown) in the conventional base to drive the rotary drum10at a slow speed of rotation.

The cylindrical body12is preferably formed of at least three cylindrical segments20,22, and24. The first segment20is an intake segment configured with an intake opening26for the intake of high temperature granular product having a high moisture content. The intake segment20includes a first series of helically arranged internal vanes28disposed on an inner surface30for moving the granular product longitudinally through the intake segment20from the intake opening26to the second segment22.

The second segment22is a blending segment configured for the blending of the granular product in a cascading manner. The blending segment22including a second series of helically arranged internal vanes32on an inner surface34for moving the granular product longitudinally through the blending segment22from the intake segment20to the third segment24. Preferably, multiple internal vanes32are disposed in a compound helix on the inner surface34, to achieve a greater efficiency in moving the granular product through the blending segment22.

A plurality of scoops36are disposed on the inner surface34adjacent to, and along the length of, the second series of internal vanes30. As best seen inFIG. 2, the spacing of the scoops36is selected such that the scoops36are spaced along the discharge side of the second series of internal vanes30, at regular intervals about the longitudinal axis of the blending segment22.

Each scoop36in the blending segment22consists of a base plate38fixed perpendicular to the inner surface34, longitudinally aligned with the center axis of the rotary drum10. Each base plate38terminates with an angled flange40disposed on a radially inward edge, oriented in the direction of rotation about the central axis of the rotary drum10. As granular product flows longitudinally through the blending segment22along each internal vane30in response to the counter-clockwise rotation of the rotary drum10, the granular product accumulates against the base plate38of each scoop36. The angled flange40, orientated in the direction of rotation, holds a portion of the granular product against the flat base portion38as the rotation of the rotary drum10lifts the granular product around the axis of rotation. As each scoop36approaches the highest point of rotation about the longitudinal axis of the rotary drum10, the retained granular product spills of the angled flange40, and cascades back to the lower portion of the blending segment22, where it is re-mixed and blended with additional sand entering the blending segment22. As the granular product cascades through the blending segment22, the overall temperature and moisture content of the granular product is reduced through evaporation and heat loss.

Turning toFIG. 3, the third segment24of the rotary drum10is a discharge segment configured for the collection of airborne dusts and fines in the rotary drum10and the discharge of cooled and blended granular product through a discharge opening48. The discharge segment24consists of three concentric cylinders50,52, and54and is contained within a conventional sand and dust collection hood100, such as shown in U.S. Pat. No. 4,981,581 to Didion, herein incorporated by reference. The first cylinder50is defined by the cylindrical drum body12, and includes a plurality of equidistantly spaced discharge ports56disposed in three sets denoted56A,56B, and56C, along the longitudinal axis of the discharge segment24. A third series of helically arranged internal vanes57is disposed on an inner surface58of the first cylinder50for moving the granular product longitudinally through the discharge segment24from the blending segment22to a discharge opening48.

Adjacent each discharge port56A in the first set, on the inner surface58of the first concentric cylinder50is a scoop59. As best seen inFIG. 4, the spacing of the scoops59is selected such that the scoops59are at regular intervals about the longitudinal axis of the blending segment22, corresponding to the placement of the discharge ports56A. Each scoop59in the discharge segment24consists of a base plate61fixed perpendicular to the inner surface58, longitudinally aligned with the center axis of the rotary drum10. Alternating base plates61terminate with an angled flange63disposed on a radially inward edge, oriented in the direction of rotation about the central axis of the rotary drum10.

At the second set of discharge ports56B, scoops59consisting of both a base plate61and an angled flange63are disposed adjacent alternating discharge ports56, as best seen in FIG.5. In addition, each discharge port56B in the second set is covered by a mesh grill65having openings of a predetermined size for the passage of a portion of the granular product.

At the third set of discharge ports56C, no scoops are present, and the openings are fully exposed, permitting passage of granular product into and out of the first concentric cylinder50.

As granular product flows through the first concentric cylinder of the discharge segment24, portions thereof are either directed by the scoops59through the discharge ports56A or56B, or is carried up and cascaded downward for cooling and blending by the rotation of the rotary drum10about the central axis.

Axially disposed with in the first cylinder50of the discharge segment24, the second cylinder52defines an axial air duct configured to convey a longitudinal cooling air flow from a positive air flow external source, preferably adjacent the discharge opening48, to the blending segment22. A set of reverse helical vanes53is disposed within the axial air duct52, adjacent the air discharge end in the blending segment22. The reverse helical vanes53are configured to redirect any granular product falling into the air duct52back out into the blending segment22. The longitudinal cooling air flow is directed counter to the longitudinal movement of the granular product through the rotary drum10, and is exhausted out the intake opening26in the intake segment20. As the longitudinal counter flow of air moves through the blending segment22and the intake segment20, heat and moisture is absorbed from the granular product and conveyed out, cooling and drying the granular product as it cascades through the blending segment22.

The third concentric cylinder54is disposed radially outward from the first cylinder50of the discharge segment24. The third concentric cylinder54comprises a cylindrical screen60which is secured to the exterior surface62of the first cylinder50by an intake side radial flange64and a discharge side radial flange66, defining a cylindrical chamber68between the first concentric cylinder50and the third concentric cylinder54. Gussets67between the intake side radial flange64and the exterior surface62provide additional strength. The cylindrical chamber68is in communication with the interior of the first concentric cylinder50through the discharge ports56A,56B, and56C for the entrance of granular product. The cylindrical screen60is selected to pass granular product particles which are smaller than a predetermined size, such as those which are suitable for re-use in a mold casting process. A series of helically arranged external vanes70are disposed on the exterior surface62of the first cylinder50, within the cylindrical chamber68. The external vanes70are configured such that the rotation of the rotary drum10will urge larger granular product particles contained within the cylindrical chamber68towards the discharge opening48.

Cylindrical screen60is further configured to permit a radial flow of air from the lower region of the conventional sand and dust collection hood100into the cylindrical chamber68, and a radial flow of air from the cylindrical chamber68into the upper region of the conventional sand and dust collection hood100. The radial inward and upward flow of air passes through the cylindrical screen60radially counter flow to the outward movement of granular product particles, and into the cylindrical chamber68. The flow of air then continues around the external vanes70and through the discharge ports56, into the interior of the first concentric cylinder50. Continuing upward, the flow of air move around the second concentric cylinder52and follows the reverse sequence to exit at the upper portion of the conventional sand and dust collection hood100. As the flow air passes radially through the cylindrical chamber68, it entrains sand fines and dust, and absorbs additional quantities of heat and moisture from the granular product, which are then evacuated from the rotary drum10for filtering and recovery.

In an alternate embodiment, suitable for demanding cooling and moisture reduction applications, a conventional blower or fan (not shown) can be coupled to the lower portion of the conventional sand and dust collection hood100to provide for a more upward positive airflow in and through the discharge segment24.

Additionally included within the discharge segment24of the preferred embodiment are a plurality of reverse scoop assemblies80and discharge scoop assemblies82. As seen inFIG. 6, each reverse scoop assembly80consists of scoop81and a reverse blade81a. Each reverse scoop assembly80is configured to redirect granular product within the discharge segment24, which has not yet passed through the cylindrical screen60back within the discharge segment24for additional circulation and break-down.

Each discharge scoop assembly82, shown inFIG. 7, is disposed adjacent the discharge opening48of the discharge segment24, and consists of a first inclined plate94disposed in the cylindrical chamber68, and a second inclined plate96disposed adjacent the inner surface58. The first inclined plate94is configured to direct granular product accumulating adjacent thereto within the cylindrical chamber68in a radially inward direction, towards the discharge opening48. Correspondingly, the second inclined plate96is configured to direct granular product accumulating adjacent thereto within the first concentric cylinder radially inward and towards the discharge opening48, where it is discharged from the rotary drum10.

Returning toFIG. 1, during operation of the rotary drum10of the present invention, heated and wet granular product is conveyed to the intake opening26and deposited within the intake segment20. Rotating motion of the rotary drum10causes the a first series of helically arranged internal vanes28to mix and homogenize the granular product thoroughly, and to move it longitudinally through the intake segment20towards the blending segment22. As the sand cascades downstream through the main blending segment22of the rotary drum, the counter flow of air passing therethrough from the air duct52evaporates moisture present in the sand, cooling it. The rotating, lifting, and cascading action of the second series of helically arranged internal vanes30and scoops36provides constant exposure of fresh surface area to the longitudinal counter flow of air to achieve a high degree of sand cooling. Additionally, the back blending and intermixing within the blending segment22blends the various zones of the granular product such that the granular product is consistent in temperature and moisture content upon exiting the blending segment22and entering the discharge segment24.

Once in the discharge segment24, portions of the granular product are urged through the discharge ports56A,56B, and56C by the interaction of the third series of helically arranged internal vanes57and the scoops59. Portions of granular product passing through the discharge ports56A and56B and into the cylindrical chamber68passes downward through the cylindrical screen60and exits the rotary drum10. Particles of granular product which are to large to pass through the cylindrical screen60are urged towards the discharge end of the rotary drum10by the series of helically arranged external vanes70. At the discharge end, the remaining granular product, generally consisting of particles to large to pass through the cylindrical screen60, is discharged from the rotary drum10by interaction with the discharge scoops82disposed adjacent the discharge opening48.

To further cool and dry the granular product, and to remove fines or dusts contained therein, a second counter flow of air is directed through the granular product in the discharge chamber24. The second counter flow of air generally enters the discharge chamber through the lower portion of the conventional sand and dust collection hood, passes through the cylindrical screen60, and into the discharge ports56A,56B, and56C below the axis of the rotary drum10. The air circulates around the coaxial air duct52, and passes upward through the discharge ports56A,56B, and56C above the axis of the rotary drum, again passing through the cylindrical chamber68and exiting the discharge chamber24through the upper portion of the conventional sand and dust collection hood100, carrying with it entrained particles, dust, moisture, and absorbed heat from the granular product. The duct52is a solid cylindrical member. Generally, it does not have any vents therethrough. On the other hand, in an alternative embodiment, one or more screens may be provided within the air duct52, and allow some air to circulate through it, to remove dust. But, in the preferred embodiment, the air duct52will be opened only at its ends.