Abstract:
A dual belt conveyor includes a pair of flexible endless loop conveyor belts arranged at an incline with a lower flight of the upper belt in face-to-face conveying relationship with an upper flight of the lower belt to retain and convey granular material between the belts. Drive pulleys are connected to both belts to move the belts at the same speed, and the conveying flights of the belts are journaled through a trough which forces the belts into a curved concave orientation between the side edges with the upper belt biased downwardly into engagement with product on the lower belt to retain product therebetween.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]    This application claims the benefit of U.S. Provisional Application Ser. No. 60/211,416, filed Jun. 14, 2000. 
     
    
     
       STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT  
         [0002]    (Not applicable)  
         BACKGROUND OF THE INVENTION  
         [0003]    (1) Field of the Invention  
           [0004]    The present invention relates generally to sandwich belt endless conveyor systems, and more particularly to an improved sandwich belt conveyor system which will carry large volume of product up very steep slopes without loss of product or damage to the product.  
           [0005]    (2) Background Information  
           [0006]    Belt conveyors have been utilized for many years to transport bulk materials, including granular materials, between various levels. However, single belt conveyors are restricted to a very shallow angle, because of the back flow of material being conveyed.  
           [0007]    To overcome this problem, a pair of dual endless flexible conveyor belts are engaged in face to face relationship to trap the bulk material therebetween and convey the bulk material at very steep vertical angles. These dual belt systems, commonly referred to as sandwich belt systems, have taken on various forms to convey bulk materials. For example, U.S. Pat. No. 3,910,405 to Couperus et al., discloses a first belt with raised edges which engage and seal with the edges of a second belt. A plurality of protruding cleats on the belt assist in carrying bulk granular material along a steep slope.  
           [0008]    U.S. Pat. No. 4,195,724 to Janitsch discloses a sandwich belt conveyor utilizing staggered rollers to urge the edges of the belts into engagement with one another to reduce leakage or spillage of material. The edges of the belts are stretched in following a sinuous path between the edge rollers, causing the confronting belt edges to firmly engage one another.  
           [0009]    U.S. Pat. No. 4,585,118 to Plaut discloses a sandwich belt system with special rollers designed to provide automatic tracking and centering of the belts of a dual belt conveyor system.  
           [0010]    While such sandwich belt systems have been effectively utilized to transport sludge, sewage, slurry-type materials and solid or semi-solid bulk material, they still have a number of problems when used for transporting granular materials such as seed and the like. The main problem of prior art sandwich belt systems is in the squeezing pressure between the belts in order to carry the granular material up steep inclines. If the belts are squeezed together too tightly, the seed can be damaged. On the other hand, if the belts are not squeezed tightly enough together, the seed can escape from between the belts.  
         BRIEF SUMMARY OF THE INVENTION  
         [0011]    It is therefore a general object of the present invention to provide an improved sandwich belt conveyor system.  
           [0012]    Another object of the present invention is to provide a sandwich belt conveyor system which will carry large volumes of granular product up very steep inclines, without damage to the granular product.  
           [0013]    A further object is to provide a sandwich belt conveyor system which will carry large volumes of granular product up steep inclines without loss of product.  
           [0014]    These and other objects of the present invention will be apparent to those skilled in the art.  
           [0015]    The dual belt conveyor of the present invention includes a pair of flexible endless loop conveyor belts arranged at an incline with a lower flight of the upper belt in face-to-face conveying relationship with an upper flight of the lower belt to retain and convey granular material between the belts. Drive pulleys are connected to both belts to move the belts at the same speed, and the conveying flights of the belts are journaled through a trough which forces the belts into a curved concave orientation between the side edges with the upper belt biased downwardly into engagement with product on the lower belt to retain product therebetween. 
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0016]    The preferred embodiments of the invention are illustrated in the accompanying drawings, in which similar or corresponding parts are identified with the same reference numeral throughout the several views, and in which:  
         [0017]    [0017]FIG. 1 is a side schematic view of the conveyor system of the present invention;  
         [0018]    [0018]FIG. 2 is an enlarged schematic view of the elbow of the schematic of FIG. 1 showing the orientations and arrangements of the belts and drive mechanism;  
         [0019]    [0019]FIG. 3A is an elevational view of the acorn pulley of the systems, taken at lines  3 - 3  in FIG. 2;  
         [0020]    [0020]FIG. 3B is a view similar to  3 A, but with granular product engaged between the belts;  
         [0021]    [0021]FIG. 4 is an enlarged sectional view taken at lines  4 - 4  in FIG. 1; and  
         [0022]    [0022]FIG. 5 is an enlarged sectional view similar to FIG. 4, but showing a second embodiment of the conveyor system. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]    Referring now to the drawings, and more particularly to FIG. 1, the squeeze belt conveyor system of the present invention is designated generally at  10  and includes a pair of upper and lower endless loop belts  12  and  14  extending through a conveyor hopper  16  to carry product from an input end  16   a  to a discharge end  16   b . Conveyor hopper  16  is oriented at a steep incline relative to a horizontal, at an angle much greater than possible with a single belt conveyor system.  
         [0024]    An elbow  18  connects the lower input end  16   a  of conveyor hopper  16  to a generally horizontally oriented infeed hopper  20 . Product to be conveyed by conveyor system  10  is input in infeed hopper  20  and conveyed to elbow  18  and thence through conveyor hopper discharge end  16   b , as described in more detail described in more detail hereinbelow.  
         [0025]    Referring now to FIG. 2, a drive assembly  22  is operably mounted within elbow  18 , to drive upper and lower belts  12  and  14  respectively. Drive assembly  22  includes a pair of drive rollers  24  and  26  extending parallel to one another between a pair of side walls of elbow  18 . One end of upper belt  12  is looped around drive roller  24 , while a portion of lower belt  14  engages drive roller  26 , to thereby drive upper and lower belts  12  and  14  respectively. Preferably, drive rollers  24  and  26  are connected (not shown) so as to rotate at the same rate, to thereby drive upper and lower belts  12  and  14  at the same speed.  
         [0026]    A special acorn pulley  28  is disposed adjacent the lower end of conveyor hopper  16 , and is located parallel to and between drive rollers  24  and  26 . A lower conveying flight  12   a  of upper belt  12  extends from drive roller  24  and thence under acorn pulley  28  before proceeding upwardly through conveyor hopper  16 . An upper conveying flight  14   a  of lower belt  14  extends from infeed hopper  20 , thence into engagement with acorn pulley  28 , and thence upwardly through conveyor hopper  16 . In this way, the two conveying flights  12   a  and  14   a  of upper and lower belts  12  and  14  pass around acorn pulley  28  immediately prior to movement through conveyor hopper  16 .  
         [0027]    As shown in FIGS. 3 a  and  3   b , an end view of acorn pulley  28  is shown, with upper belt lower flight  12   a  engaging lower belt upper flight  14   a  as they pass around acorn pulley  28 . Acorn pulley  28  includes a pair of cone-shaped acorns  30  at each end of pulley shaft  32 , the acorns having their largest diameters at the outward ends of shaft  32  and tapering inwardly therefrom. As shown in FIG. 3 a , belt flights  12   a  and  14   a  contact one another in a generally flat flush condition as they travel around acorn pulley  28  with the belts riding on the largest diameter of acorns  30 . As granular product  34  is added on top of lower belt upper flight  14   a , the central portions of belt flights  12   a  and  14   a  will separate from one another as product  34  is gently squeezed between the belts. As shown in FIG. 3 b  the edges of the belts will curve to conform to the sloped surfaces of acorns  30  as product  34  grows in volume between the belts.  
         [0028]    Referring once again to FIG. 2, it can be seen that lower belt  14  is looped around a pair of free rolling tail pulleys  36  and  38  located at forward and rearward ends of infeed hopper  20 . More specifically, the lower return flight  14   b  of lower belt  14  exits the input end  16   a  of conveyor hopper  16 , travels around the lower belt drive roller  26 , thence around tail pulley  36 , and then extends the length of infeed hopper  20  and is looped around tail pulley  38  before extending to acorn pulley  28  as the upper flight  14   a  of lower belt  14 . Granular product is deposited on the lower belt upper flight  14   a  in infeed hopper  20 , which carries the product to acorn pulley  28  at the input end of conveyor hopper  16 . As discussed above, upper belt lower flight then engages the upper surface of lower belt upper flight  14   a  to squeeze the product between the belts, as the belts pass around acorn pulley  28 . As shown in FIG. 1, the sandwiched flights of belts  12  and  14  extend upwardly through conveyor hopper  16  to discharge end  16   b . At discharge end  16   b , lower belt upper flight  14   a  traverses downwardly around tail pulley  40 , thereby separating the lower belt upper flight from the upper belt lower flight and discharging product from between the sandwiched flights. Upper belt lower flight  12   a  continues upward to tail pulley  42 , where it traverses upwardly around the tail pulley. Upper belt upper flight  12   b  and lower belt lower flight  14   b  then return downwardly through conveyor hopper  16  on the return run of each belt.  
         [0029]    Referring now to FIG. 4, hopper  16  is preferably an elongated rectangular tube  44  having top and bottom walls  44   a  and  44   b , and opposing side walls  44   c . A trough  46  is formed within tube  44  through which flights  12   a  and  14   a  of upper and lower belts  12  and  14  will slide as they convey product  34  therebetween. The inventors herein have found that the use of a generally U-shaped trough  46  having upper leg portions  46   a  and  46   b  with upper ends sloped towards one another will cause upper belt lower flight  12   a  to be forced into a curved orientation pressing downwardly against product  34  and lower belt upper flight  14   a . As can be seen in FIG. 4, the width of trough  46  between upper legs  46   a  and  46   b  is less than the width of belts  12  and  14  (which may be seen in their respective return flights  12   b  and  14   b  above and below trough  46 ). As additional product is added between the belts, the upper belt lower flight is raised thereby further increasing the curvature and pressure of the upper belt against the product. Lower portions  46   c  and  46   d  of the legs of trough  46  have lower ends which slope inwardly and are connected to horizontal base  46   e  of trough  46 . It can be seen that the slope of the lower end of leg lower portions  46   c  and  46   d  also supports the curvature of lower belt upper flight  14   a  as it slides along trough  46 .  
         [0030]    The upper ends of trough leg upper portions  46   a  and  46   b  are connected to the tube side walls  44   c  and  44   d  respectively, by coplanar shelves  48 . Shelves  48  will retain the return flight  12   b  of upper belt  12  on its return from the discharge end of conveyor hopper  16 . A space between trough  46  and tube bottom wall  44   b  will receive the return flight  14   b  of lower belt  14 .  
         [0031]    Referring now to FIG. 5, a second embodiment of the conveyor hopper is designated generally  116 . In this second embodiment, a cylindrical tube  146  serves as both the trough  46  and tube  44  used in the first embodiment shown in FIG. 4. The return flights  12   b  and  14   b  of belts  12  and  14  are then returned exteriorly of the tubular trough  146 , after looping around upper and lower rollers  150  and  152  respectively.  
         [0032]    Belts  12  and  14  have a width which is greater than the diameter of tubular trough  146 , such that upper portions  146   a  and  146   b  (located above a horizontal diameter of tubular trough  146 ) serve the same inwardly sloping function as trough upper leg portions  46   a  and  46   b  of the first embodiment, shown in FIG. 4. Because the width of belts  12  and  14  is greater than the diameter of trough  146 , the conveying flights  12   a  and  14   a  of belts  12  and  14 , within trough  146 , will be forced into a curved shaped by hopper sloped portions  146   a  and  146   b . As with the first embodiment, this curved shape forces upper belt lower flight  12   a  downward into contact with product  34  and against lower belt upper flight  14   a , to retain product  34  securely therebetween as it is conveyed upwardly at a steep incline through conveyor hopper  116 .  
         [0033]    Whereas the invention has been shown and described in connection with the preferred embodiment thereof, many modifications, substitutions and additions may be made which are within the intended broad scope of the appended claims.