Abstract:
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.

Description:
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. 

   
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     In the accompanying drawings which form part of the specification: 
       FIG. 1  is a longitudinal sectional view of a rotary cooling, blending, and screening drum; 
       FIG. 2  is a cross sectional view of the rotary cooling, blending, and screening drum of  FIG. 1 , taken at line  2 — 2 ; 
       FIG. 3  is an enlarged view of the discharge segment of the rotary cooling, blending, and screening drum of  FIG. 1 ; 
       FIG. 4  is a cross sectional view of the rotary cooling, blending, and screening drum of  FIG. 1 , taken at line  4 — 4 ; 
       FIG. 5  is a cross sectional view of the rotary cooling, blending, and screening drum of  FIG. 1 , taken at line  5 — 5 ; and 
       FIG. 6  is a component view of the reverse scoop assembly within the discharge segment taken along the line  6 — 6  of  FIG. 3 ; and 
       FIG. 7  is a component view of the discharge scoop assembly taken along the line  7 — 7  of FIG.  3 . 
   

   Corresponding reference numerals indicate corresponding parts throughout the several figures of the 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 to  FIG. 1 , a rotary drum of the present invention for effecting the blending and cooling of granular product is shown generally at  10 . The rotary media drum  10  comprises a cylindrical drum body  12 , which is includes a plurality of spaced circumferential drum assembly tires  14  disposed on an external surface  16 . The circumferential drum assembly tires support the rotary drum  10  on a conventional base (not shown). Correspondingly, a circumferential sprocket  18  on the external surface  16  engages a conventional drive mechanism (not shown) in the conventional base to drive the rotary drum  10  at a slow speed of rotation. 
   The cylindrical body  12  is preferably formed of at least three cylindrical segments  20 ,  22 , and  24 . The first segment  20  is an intake segment configured with an intake opening  26  for the intake of high temperature granular product having a high moisture content. The intake segment  20  includes a first series of helically arranged internal vanes  28  disposed on an inner surface  30  for moving the granular product longitudinally through the intake segment  20  from the intake opening  26  to the second segment  22 . 
   The second segment  22  is a blending segment configured for the blending of the granular product in a cascading manner. The blending segment  22  including a second series of helically arranged internal vanes  32  on an inner surface  34  for moving the granular product longitudinally through the blending segment  22  from the intake segment  20  to the third segment  24 . Preferably, multiple internal vanes  32  are disposed in a compound helix on the inner surface  34 , to achieve a greater efficiency in moving the granular product through the blending segment  22 . 
   A plurality of scoops  36  are disposed on the inner surface  34  adjacent to, and along the length of, the second series of internal vanes  30 . As best seen in  FIG. 2 , the spacing of the scoops  36  is selected such that the scoops  36  are spaced along the discharge side of the second series of internal vanes  30 , at regular intervals about the longitudinal axis of the blending segment  22 . 
   Each scoop  36  in the blending segment  22  consists of a base plate  38  fixed perpendicular to the inner surface  34 , longitudinally aligned with the center axis of the rotary drum  10 . Each base plate  38  terminates with an angled flange  40  disposed on a radially inward edge, oriented in the direction of rotation about the central axis of the rotary drum  10 . As granular product flows longitudinally through the blending segment  22  along each internal vane  30  in response to the counter-clockwise rotation of the rotary drum  10 , the granular product accumulates against the base plate  38  of each scoop  36 . The angled flange  40 , orientated in the direction of rotation, holds a portion of the granular product against the flat base portion  38  as the rotation of the rotary drum  10  lifts the granular product around the axis of rotation. As each scoop  36  approaches the highest point of rotation about the longitudinal axis of the rotary drum  10 , the retained granular product spills of the angled flange  40 , and cascades back to the lower portion of the blending segment  22 , where it is re-mixed and blended with additional sand entering the blending segment  22 . As the granular product cascades through the blending segment  22 , the overall temperature and moisture content of the granular product is reduced through evaporation and heat loss. 
   Turning to  FIG. 3 , the third segment  24  of the rotary drum  10  is a discharge segment configured for the collection of airborne dusts and fines in the rotary drum  10  and the discharge of cooled and blended granular product through a discharge opening  48 . The discharge segment  24  consists of three concentric cylinders  50 ,  52 , and  54  and is contained within a conventional sand and dust collection hood  100 , such as shown in U.S. Pat. No. 4,981,581 to Didion, herein incorporated by reference. The first cylinder  50  is defined by the cylindrical drum body  12 , and includes a plurality of equidistantly spaced discharge ports  56  disposed in three sets denoted  56 A,  56 B, and  56 C, along the longitudinal axis of the discharge segment  24 . A third series of helically arranged internal vanes  57  is disposed on an inner surface  58  of the first cylinder  50  for moving the granular product longitudinally through the discharge segment  24  from the blending segment  22  to a discharge opening  48 . 
   Adjacent each discharge port  56 A in the first set, on the inner surface  58  of the first concentric cylinder  50  is a scoop  59 . As best seen in  FIG. 4 , the spacing of the scoops  59  is selected such that the scoops  59  are at regular intervals about the longitudinal axis of the blending segment  22 , corresponding to the placement of the discharge ports  56 A. Each scoop  59  in the discharge segment  24  consists of a base plate  61  fixed perpendicular to the inner surface  58 , longitudinally aligned with the center axis of the rotary drum  10 . Alternating base plates  61  terminate with an angled flange  63  disposed on a radially inward edge, oriented in the direction of rotation about the central axis of the rotary drum  10 . 
   At the second set of discharge ports  56 B, scoops  59  consisting of both a base plate  61  and an angled flange  63  are disposed adjacent alternating discharge ports  56 , as best seen in FIG.  5 . In addition, each discharge port  56 B in the second set is covered by a mesh grill  65  having openings of a predetermined size for the passage of a portion of the granular product. 
   At the third set of discharge ports  56 C, no scoops are present, and the openings are fully exposed, permitting passage of granular product into and out of the first concentric cylinder  50 . 
   As granular product flows through the first concentric cylinder of the discharge segment  24 , portions thereof are either directed by the scoops  59  through the discharge ports  56 A or  56 B, or is carried up and cascaded downward for cooling and blending by the rotation of the rotary drum  10  about the central axis. 
   Axially disposed with in the first cylinder  50  of the discharge segment  24 , the second cylinder  52  defines an axial air duct configured to convey a longitudinal cooling air flow from a positive air flow external source, preferably adjacent the discharge opening  48 , to the blending segment  22 . A set of reverse helical vanes  53  is disposed within the axial air duct  52 , adjacent the air discharge end in the blending segment  22 . The reverse helical vanes  53  are configured to redirect any granular product falling into the air duct  52  back out into the blending segment  22 . The longitudinal cooling air flow is directed counter to the longitudinal movement of the granular product through the rotary drum  10 , and is exhausted out the intake opening  26  in the intake segment  20 . As the longitudinal counter flow of air moves through the blending segment  22  and the intake segment  20 , heat and moisture is absorbed from the granular product and conveyed out, cooling and drying the granular product as it cascades through the blending segment  22 . 
   The third concentric cylinder  54  is disposed radially outward from the first cylinder  50  of the discharge segment  24 . The third concentric cylinder  54  comprises a cylindrical screen  60  which is secured to the exterior surface  62  of the first cylinder  50  by an intake side radial flange  64  and a discharge side radial flange  66 , defining a cylindrical chamber  68  between the first concentric cylinder  50  and the third concentric cylinder  54 . Gussets  67  between the intake side radial flange  64  and the exterior surface  62  provide additional strength. The cylindrical chamber  68  is in communication with the interior of the first concentric cylinder  50  through the discharge ports  56 A,  56 B, and  56 C for the entrance of granular product. The cylindrical screen  60  is 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 vanes  70  are disposed on the exterior surface  62  of the first cylinder  50 , within the cylindrical chamber  68 . The external vanes  70  are configured such that the rotation of the rotary drum  10  will urge larger granular product particles contained within the cylindrical chamber  68  towards the discharge opening  48 . 
   Cylindrical screen  60  is further configured to permit a radial flow of air from the lower region of the conventional sand and dust collection hood  100  into the cylindrical chamber  68 , and a radial flow of air from the cylindrical chamber  68  into the upper region of the conventional sand and dust collection hood  100 . The radial inward and upward flow of air passes through the cylindrical screen  60  radially counter flow to the outward movement of granular product particles, and into the cylindrical chamber  68 . The flow of air then continues around the external vanes  70  and through the discharge ports  56 , into the interior of the first concentric cylinder  50 . Continuing upward, the flow of air move around the second concentric cylinder  52  and follows the reverse sequence to exit at the upper portion of the conventional sand and dust collection hood  100 . As the flow air passes radially through the cylindrical chamber  68 , 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 drum  10  for 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 hood  100  to provide for a more upward positive airflow in and through the discharge segment  24 . 
   Additionally included within the discharge segment  24  of the preferred embodiment are a plurality of reverse scoop assemblies  80  and discharge scoop assemblies  82 . As seen in  FIG. 6 , each reverse scoop assembly  80  consists of scoop  81  and a reverse blade  81 a. Each reverse scoop assembly  80  is configured to redirect granular product within the discharge segment  24 , which has not yet passed through the cylindrical screen  60  back within the discharge segment  24  for additional circulation and break-down. 
   Each discharge scoop assembly  82 , shown in  FIG. 7 , is disposed adjacent the discharge opening  48  of the discharge segment  24 , and consists of a first inclined plate  94  disposed in the cylindrical chamber  68 , and a second inclined plate  96  disposed adjacent the inner surface  58 . The first inclined plate  94  is configured to direct granular product accumulating adjacent thereto within the cylindrical chamber  68  in a radially inward direction, towards the discharge opening  48 . Correspondingly, the second inclined plate  96  is configured to direct granular product accumulating adjacent thereto within the first concentric cylinder radially inward and towards the discharge opening  48 , where it is discharged from the rotary drum  10 . 
   Returning to  FIG. 1 , during operation of the rotary drum  10  of the present invention, heated and wet granular product is conveyed to the intake opening  26  and deposited within the intake segment  20 . Rotating motion of the rotary drum  10  causes the a first series of helically arranged internal vanes  28  to mix and homogenize the granular product thoroughly, and to move it longitudinally through the intake segment  20  towards the blending segment  22 . As the sand cascades downstream through the main blending segment  22  of the rotary drum, the counter flow of air passing therethrough from the air duct  52  evaporates moisture present in the sand, cooling it. The rotating, lifting, and cascading action of the second series of helically arranged internal vanes  30  and scoops  36  provides 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 segment  22  blends the various zones of the granular product such that the granular product is consistent in temperature and moisture content upon exiting the blending segment  22  and entering the discharge segment  24 . 
   Once in the discharge segment  24 , portions of the granular product are urged through the discharge ports  56 A,  56 B, and  56 C by the interaction of the third series of helically arranged internal vanes  57  and the scoops  59 . Portions of granular product passing through the discharge ports  56 A and  56 B and into the cylindrical chamber  68  passes downward through the cylindrical screen  60  and exits the rotary drum  10 . Particles of granular product which are to large to pass through the cylindrical screen  60  are urged towards the discharge end of the rotary drum  10  by the series of helically arranged external vanes  70 . At the discharge end, the remaining granular product, generally consisting of particles to large to pass through the cylindrical screen  60 , is discharged from the rotary drum  10  by interaction with the discharge scoops  82  disposed adjacent the discharge opening  48 . 
   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 chamber  24 . 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 screen  60 , and into the discharge ports  56 A,  56 B, and  56 C below the axis of the rotary drum  10 . The air circulates around the coaxial air duct  52 , and passes upward through the discharge ports  56 A,  56 B, and  56 C above the axis of the rotary drum, again passing through the cylindrical chamber  68  and exiting the discharge chamber  24  through the upper portion of the conventional sand and dust collection hood  100 , carrying with it entrained particles, dust, moisture, and absorbed heat from the granular product. The duct  52  is 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 duct  52 , and allow some air to circulate through it, to remove dust. But, in the preferred embodiment, the air duct  52  will be opened only at its ends. 
   In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.