Abstract:
A bottom unloader for conveying feed material from a silo is disclosed. The unloader may have a housing with a drive unit and discharge, a conveyor positioned in the trough of a silo and a rotating cutter arm. The bottom unloader may be equipped with heavy-duty hooks having a wide uniform forward profile to prevent breaking and clogging of the conveyor. The hooks may be arranged in a repeating sequence to optimize unloading. The silo trough may have a wide chamfered section to prevent bridging. A discharge cover may extend from the conveyor to cover the top of the trough within the silo. The discharge cover remains fixed to conveyor backbone and is removed from the silo with conveyor.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/813,562 filed Jun. 14, 2006, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to silo unloaders, and more particularly relates to bottom unloaders with improved performance and efficiency. 
     BACKGROUND INFORMATION 
     Conventionally, silage and other feed materials are stored in structures such as silos. The feed material is often removed from the structure by way of a bottom unloader. A conventional bottom unloader is described in U.S. Pat. No. 2,635,770 to Tiedemann, which is herein incorporated by reference. 
     Conventional bottom unloaders suffer from several disadvantages, including chain clogging which requires starting and stopping the unloader in forward and reverse directions to free the chain. This process often leads to breaking the chain, requiring removal of the unloader and repair of the chain. Other disadvantages of conventional bottom unloaders include low feed rates, inability to convey hailage at moisture levels above 50%, high maintenance costs and high utility costs. Furthermore, the unreliability of the bottom unloaders requires an operator to stay with the machine during unloading to prevent clogging. 
     The present invention has been developed in view of the foregoing. 
     SUMMARY OF THE INVENTION 
     The present invention provides a bottom unloader for conveying feed material from a silo. The unloader may have a housing with a drive unit and discharge, a conveyor positioned in the trough of a silo and a rotating cutter arm. The bottom unloader may be equipped with heavy-duty hooks having a wide uniform forward profile to prevent breaking and clogging of the conveyor. The hooks may be arranged in a repeating sequence to optimize unloading. The silo trough may have a wide chamfered section to prevent bridging. A discharge cover may extend from the conveyor to cover the top of the trough within the silo. The discharge cover remains fixed to the conveyor backbone and is removed from the silo with conveyor. 
     An aspect of the present invention provides a chain for a cutter or conveyor arm of a silo bottom unloader comprising an endless chain and hooks mounted on and extending generally laterally from the cutter chain, wherein each hook has a forward profile in which the base of the cutter hook has a width that is substantially equal to or greater than the remainder of the cutter hook. 
     Another aspect of the present invention provides a bottom unloading system for a silo comprising a housing for a drive unit and discharge outlet, a conveyor attached at its proximal end to the housing having an endless conveyor chain structured to rotate longitudinally about the conveyor, conveyor hooks mounted on and extending radially from the conveyor chain, a cutter arm rotatably mounted on a distal end of the conveyor having an endless cutter chain structured to rotate longitudinally about the cutter arm; and cutter hooks extending generally laterally from the cutter chain, wherein each cutter hook has a forward profile in which the base of the cutter hook has a width that is substantially equal to or greater than the remainder of the cutter hook. 
     A further aspect of the present invention provides a bottom unloading system for a silo comprising a housing for a drive unit and discharge outlet, backbone extending from the housing, a discharge cover attached to and extending from the housing, a conveyor supported by the backbone and attached to the housing, a cutter arm rotatably mounted on a distal end of the conveyor. 
     Yet another aspect of the present invention provides a cutter hook for a cutter arm chain of a silo bottom unloader, the cutter hook comprising a proximal leg and a distal hook portion, wherein the leg has a width measured from a forward profile of the cutter hook, the hooked portion has a width measured from the forward profile, and the width of the leg is greater than or substantially equal to the width of the hooked portion. 
     These and other aspects will become more apparent from the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a silo bottom unloader prior to being installed in the silo according to one embodiment of the present invention. 
         FIG. 2  is a top cross-sectional view of a silo with a bottom unloader installed therein according to one embodiment of the present invention. The silo is shown as empty for illustrative purposes. 
         FIG. 3  is a partially schematic side view of a series of adjacent cutter chain plates having cutter hooks mounted thereon at different vertical positions according to one embodiment of the present invention. 
         FIG. 4  is a partially schematic side view of a series of adjacent conveyor chain plates having cutter hooks mounted thereon at different vertical positions according to one embodiment of the present invention. 
         FIG. 5  is a top view of a cutter hook according to one embodiment of the present invention. 
         FIG. 6  is a side view of a cutter hook according to one embodiment of the present invention. 
         FIG. 7  is a front view of a cutter hook according to one embodiment of the present invention. 
         FIG. 8  illustrates the trough and tapered section recessed within the silo floor according to one embodiment of the present invention. 
         FIG. 9  illustrates a section view of the silo floor along line  9 - 9  of  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a silo bottom unloader  1  is shown according to one embodiment of the present invention. The bottom unloader  1  has a housing  10  which holds a drive unit including a motor  12  and transmission  14 . Other parts of the housing  10  include mounting brackets  18  and a discharge outlet  16 . The discharge outlet  16  may have a hinged door  17  for opening and closing the outlet  16 . As used herein the housing  10  is the portion of the unloader  1  that holds the drive components and discharge assembly and which remains outside the silo  100  at all times. Extending from the housing  10  is a conveyor arm  30 . About the periphery of the conveyor arm  30  is an endless conveyor chain  72  comprising several conventional chain links. The motor  12  and transmission  14  couple to and power the chain  72  of the conveyor arm  30  within the housing  10 . Mounted on the conveyor chain  72  are laterally or horizontally extending conveyor hooks  70 . In one embodiment, none of the conveyor cutter hooks  70  extend from the conveyor chain  72  with a vertical component, e.g., all of the conveyor hooks  70  extend substantially horizontally. Rotatably mounted to a distal end of the conveyor arm  30  is a cutter arm  40 . Mounted about the periphery of the cutter arm  40  is an endless cutter chain  82  comprising several conventional chain links. Laterally or horizontally extending from the cutter chain  82  are cutter hooks  80 . In one embodiment, none of the cutter hooks  80  extend from the cutter chain  82  with a vertical component, e.g., all of the cutter hooks  70  extend substantially horizontally. The supporting structure of the conveyor arm  30  and cutter arm  40  is a frame often referred to as a backbone  50 . From the folded position shown in  FIG. 1 , the cutter arm  40  and conveyor arm  30  are inserted through an access door  102  of a silo  100 . A discharge cover  60  extends outwardly from a proximal portion of the backbone  50 . This discharge cover  60  rests on runners incorporated in a trough inside the silo and serves to enclose the top of the trough (not shown in  FIG. 1 ) inside of the silo  100 . The discharge cover  60  is dimensioned to span the width of the trough, which is most commonly 24 inches or 30 inches. 
     Referring to  FIG. 2 , the silo bottom unloader of  FIG. 1  is shown inserted in the bottom of the silo  100 . Arrows in  FIG. 2  indicate directional movement of the chains  72 ,  82  and cutter arm  40 . While it is possible to rotate the cutter arm  40  and chains  72 ,  82  in either direction through controls on the housing  10 , the orientation of the cutter hooks  80  makes counterclockwise rotation in this configuration preferred. As can be seen, the conveyor arm  50  sits within a trough  130  and the discharge cover  60 , which is part of or attached to the backbone  50 , rests on runners  150  (shown in  FIGS. 8-9 ) within the trough  130 . This permits 360-degree rotation of cutter arm  40  over a relatively flat surface inside the silo. Attaching the discharge cover  60  to the backbone  50  facilitates easy removal of the bottom unloader  1  from the silo especially if jamming occurs. Wiper blades  81  are preferably installed on the cutter chain  82 . The wiper blades  81  are directed upwardly and inwardly from the cutter chain  82  and prevent silage from accumulating on the top of the cutter arm  40 . Excess silage on top of the cutter arm  40  may cause the chain to bind or break, stalling the unloading process. The trough  130  terminates at the center of the silo floor  120  with a chamfered section  140 . The chamfered section  140  funnels feed material pulled inwardly by the cutter hooks  80  to the conveyor hooks  70  rotating in a lower elevation. The conveyor hooks  70  exit the silo  100 , pulling the silage through the trough  130  and under the discharge cover  60  to the discharge outlet  16  of the housing  10 . 
     Referring to  FIG. 3 , an arrangement of the cutter hooks  80  positioned on adjacent links of the cutter arm  40  are shown. The cutter hooks  80  are positioned at elevations increasing in elevation from left to right. Left to right is also the direction of travel when viewing  FIGS. 3 and 4 . The first position has a hook at a lower most elevation. For purposes of this description the leftmost position is the first position, but it should be understood that when the chain is motion this is also the trailing position. In the embodiment shown in  FIG. 3 , the cutter hooks  70  on successive links increase slightly until reaching a maximum elevation at the fifth position shown. The cutter hook  70  located in the sixth position is set at an elevation less than that of the cutter hook  70  in the fifth position.  FIG. 3  shows a preferred configuration; however, the elevation of the cutter hook  70  in the sixth position may be changed to vary the aggressiveness of the cutter chain with increased elevations of the cutter hook  70  in position six resulting in a less aggressive chain and lower elevations resulting in a more aggressive chain. The cutter hooks  70  are welded or otherwise mounted on cutter plates  90 , which attach by fastening means such as standard bolts to the links of the cutter chain  82 . The fasteners (not shown) pass through bolt holes  91  located in the cutter plates  90 . The cutter blades may have a width W 3  of about 2 to about 4 inches, for example, 3 inches. The cutter plates  90  may also have a height H 3  of about 4 to about 8 inches, for example, 6 inches. The direction of H 3  also corresponds to elevation as the term is used herein. 
     Referring to  FIG. 4 , an arrangement of conveyor hooks  70  on a series of conveyor plates  92  is shown. As with the cutter hooks  80 , the conveyor hooks  70  increase in elevation from link to link starting with a first link having a lowest elevation and increasing to a fifth link having a highest elevation. Since the conveyor is a different application, the need for adjusting the sixth position conveyor hook, as may be done with the sixth position of the cutter hooks, may not be necessary. The conveyor hooks  70  are welded or otherwise mounted on the conveyor plates  92 , which are fastened to the links of the conveyor chain  72  using standard bolts (not shown) through boltholes  93 . The conveyor plates  92  may have a width W 4  of about 2 to about 4 inches, for example, 3 inches and a height, H 4 , of about 4 to about 8 inches, for example, 5.5 inches. While the arrangements of hooks  70 ,  80  are described in sequences of five and six adjacent hooks, arrangements containing more or less hooks are possible, but in groups of no less than four. In a preferred embodiment, the conveyor hooks  70  and cutter hooks  80  extend outward from their respective chains in a horizontal or lateral direction, i.e., parallel to the silo floor. 
     Referring to  FIG. 5 , a top view of a cutter hook  80  is shown. In one embodiment, the cutter hook  80  is made from steel square stock. The square stock is bent to an angle, represented by α, of about 120 to about 145 degrees, for example 131 degrees. The bent stock is then cut to form a hooked portion  83  having a clearance face  84 . The square stock is then cut at an angle, β shown in  FIG. 5 , of about 60 to about 90 degrees, for example, 75 degrees, to provide a forward lean to the hook. The forward lean may also be produced by bending the leg  85  of the cutter hook  80 . In the embodiment shown, the cutter hook  80  is made from 1 inch square stock, bent and cut to form an hooked portion  83  and clearance face  84 , the leg  85  of the cutter hook  80  has a leading edge  86 , a trailing edge  87 , leading faces  88  and trailing faces  89 . The leg has a width from leading edge  86  to trailing edge  87 , W 5 , which is largely dependent on the starting material from which the cutter hook is made. The width W 5  may be from about 1 inch to about 2 inches, for example, 1.4 inches. The cutter hook  80  may also have a length, L 5 , as shown in  FIG. 5 , typically from about 2 inches to about 3.5 inches, for example, 2.75 inches. 
       FIGS. 6 and 7  show side and front views of the cutter hook  80 , respectively.  FIG. 7  is a view of the forward profile or leading portion of the cutter hook  80 . The cutter hook may have a width W 7  as seen in  FIG. 7 . Because square stock is preferred starting material for the hooks, the width W 7  is often, but not necessarily, equivalent to the width W 5  mentioned above in reference to  FIG. 5 . It should be noted that the width W 7  represents the widest portion of the cutter hook  80 . There is no outwardly flared portion at the top of the cutter hook adjacent the clearance space  84  and no substantial narrowing along the length of the leg  85 . This design having a stout base not only prevents the hooks from breaking, it resists the inclination of the hooks  80  to turn and twist. The hooks  80  may also have a height H 7  as shown in  FIG. 7 , typically from about 2.5 to about 5 inches, for example, 3.5 inches. 
     While  FIGS. 5 through 7  show the transition from the leg  85  to a distal portion of the cutting hook  80  as an abrupt transition represented by angle α, cutter hooks having a radius transition are also effective. It should also be noted that while square stock has been used to show a preferred embodiment, round stock or other configurations of starting material may be used so long as the base of the cutting hook  80  when viewed from the front as in  FIG. 7  is at or near the widest point of the cutting hook  80 . 
     While the above detail regarding  FIGS. 5-7  was made with reference to the cutter hooks  80 , it should be understood that the configuration has proven to be effective for conveyor hooks  70  as well. Examples of suitable materials for the cutter hooks  80  and conveyor hooks  70  include steel, iron, stainless steel and titanium, and alloys of each. A preferred embodiment utilizes extruded steel square stock for the hooks  70  and  80 . 
     Referring to  FIG. 8 , the trough  130  is shown recessed in the silo floor  120 . As mentioned above, the trough  130  extends from the access door  102  at the exterior of the silo to a central point of the silo floor  120 . At the end of the trough  130  at the center of the silo  100  is a chamfered section  140 , which is generally semi-circular and may have tapered extensions  142  providing a tapered u-shape about the bottom of the trough  130 . This chamfered section  140  along with tapered extension  142  act to funnel silage discharged from the rotating cutter arm  40  to the conveyor arm  30  positioned within the trough  130 . The chamfered section  140  may have a radius R 1  at its intersection with the bottom of the trough  130 . R 1  may be about 14 to about 16 inches, for example, 15 inches. The chamfered section  140  may have a second radius R 2  at its intersection with silo floor  120 . R 2  may be about 24 to about 26 inches, for example, 25 inches. A configuration with R 2  of 25 inches has shown to prevent bridging and loss material feed to the silo, a common problem with conventional unloaders. Also shown in  FIG. 8  are runners  150 , which support the discharge cover (not shown in  FIG. 8 ). The runners may be for example 0.25″×1″ steel extending from a sidewall of the trough  130 . 
     Referring now to  FIG. 9 , a sectional view of the trough  130  along line  9 - 9  of  FIG. 8  is shown.  FIG. 9  shows a height of the trough H 9 . H 9  may be 5 to 10 inches, for example, 7⅜ inches. The height of the chamfered section  140  is variable. However, it may be 4⅜ inches according to one embodiment of the present invention. Runners  150  are shown slightly recessed from the top of silo floor  120  to allow room for discharge cover  60 , thus providing a flush transition between the silo floor  120  and discharge cover  60 . The width of the trough  130  is also variable and depends on the conveyor or unloader used. As mentioned above 24 inch and 30 inch troughs to accommodate similarly sized unloaders are the most common. 
     As mentioned above, chain clogging is problem with many conventional bottom unloaders. Clogging requires the unloader be removed from the silo in order to be cleaned out or jogging the cutter arm in reverse then forward. The latter option risks breaking the chain which causes significant downtime and maintenance. The unloader of the present invention has demonstrated improved reliability without sacrificing unloading capability easily feeding over 150 pounds per minute of 50-60% moisture silage without clogging or requiring any operator intervention. In contrast, a conventional unloader would often feed less than 10 pounds per minute at 60% moisture and would also require frequent operator attention. The silo bottom unloader described herein avoids the clogging associated with conventional unloaders, provides the ability to unload silage with relatively high moisture content compared to silage able to be unloaded by conventional unloaders, and significantly improves unloading efficiency. As a result, animal feed time is significantly reduced. 
     Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appended claims.