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CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of a provisional patent application entitled ANTI-SLAB DEVICE filed by Michael Podoll et al. on Apr. 21, 2008, and having a Ser. No. 61/046,638, which application is hereby incorporated herein in its entirety by this reference. 
    
    
     BACKGROUND OF INVENTION 
     Spinner spreaders for particulate materials are well known for agricultural and road maintenance applications. Many of the materials to be spread are not always free flowing, such as quarried agricultural lime or sand and salt for winter road maintenance. These materials consist of varying particle sizes and shapes that cause the material particles to interlock. The flow characteristics of these materials are also affected by the handling and storing of the material to be spread. As an example, agricultural lime and sand mixtures for road maintenance applications are stored outdoors and subject to moisture. The moisture adds to material cohesion, changes the natural angle of repose and the spatula angle, and further degrades the flow characteristics. 
     Materials to be spread are typically deposited on the spinner from a material storage bin via a belt conveyor or drag conveyor. As the material falls from the conveyor to the spinner, its flow is discontinuous because the particles adhere together and fall in slabs or blocks. The phenomena are much like those noted in avalanche studies and landslides where material adheres together and falls suddenly in slumps, blocks, and slabs. The result is inconsistent flow to the spinner. With certain materials and under certain conditions of the material and the application such as slow conveying speeds, material flow to the spinner may at times cease and, when weight of the material overcomes the adhesion or shear strength, the material will fall off the conveyor in large slabs. This changing flow does not permit accurate, consistent and even spreading and also may cause stress on the spreader&#39;s hydraulics and/or mechanical systems. 
     Modern variable rate technology for agricultural spreaders requires that the conveyor adjust its speed to match the needs of predetermined nutrient prescriptions. The requirements for material can vary greatly between prescription grids, and conveyor speeds must adjust accordingly to meter the material. Slow conveyor speeds make the slabbing of material more prevalent and result in loss of precision application. 
     Prior art in spreaders include hanging chains in the material path at the end of the discharge conveyor and attempt to use the motion of the vehicle to keep material from falling in slabs. This has proven to be inconsistent and not useful for the range of materials to be spread. 
     Other prior art exists where a reel or flail spins and keeps the material flowing. This art may produce a consistent flow, but the speeds of these devices can cause material to be thrown about and not placed accurately on the spinner. As noted in Rissi U.S. Pat. No. 6,517,281, the accurate placement of material on the spinner of precision spreaders is crucial to the spread pattern. This type of device can also be damaged if foreign debris is mixed in with the material to be spread. 
     European Patent Application EP1285998 A1 teaches a linear reciprocating device with a frequency of 30 to 130 strokes per minute, a stroke that exceeds the pitch of loosening protrusions, and loosening protrusions that are fixed across the material flow. This device can snag loose debris or block an object that is too large to pass the loosening protrusions which in turn could prevent consistent flow of material. Large objects such as rocks or frozen chunks of material may also damage the device itself. Because the protrusions are frequently in the material path (especially at high conveyor speeds), they can also impede the flow of large quantities of conveyed materials. 
     Prior art in industrial conveying applications may vibrate the conveyor itself to get material to flow smoothly off the conveyor end. Any vibrators attached to the discharge end of the conveyor could also tend to compact the material in the hopper. Vibrators attached directly to conveyors or bin walls also may tend to fatigue the structure they are attached to and cause equipment failures. 
     Therefore, limitations of prior art often do not achieve the results needed for today&#39;s precision spreading. 
     SUMMARY OF THE INVENTION 
     An objective of this invention is the provision of an improved method of delivering smooth, consistent flow of material from a conveyor system. 
     Another objective of this invention is the provision of an improved method of delivering smooth, consistent flow of material from a conveyor system to allow precision spreading of agricultural or de-icing materials. 
     Another objective is a provision of an anti-slabbing device that interacts with the shear or avalanche zone of the material at the end of the discharge conveyor. 
     Another object of the device is to remove any avalanche potential of material remaining on the conveyor after the conveyor ceases movement. 
     Another objective is a provision of a simple, low power, compact device that keeps material flowing from a conveyor in a consistent fashion suitable for installation on a land application or roadway spreader. 
     Another objective is a provision of a device that can help deliver consistent flow from a discharge conveyor where the device is not attached to the discharge conveyor system and will not apply undue stress to conveyor components. 
     Another objective is a provision of a device that can move out of the way of large, solid objects that may be mixed with the conveyed material. 
     Another objective is to create a device shape in the area of material interaction where the shape will not snag foreign debris that may be mixed with the conveyed material. 
     Another objective is a provision of a device that can stow in such a manner that prevents the devices from interacting with free-flowing material. 
     Another objective is to loosen material and provide consistent material flow while reducing concern of bodily entanglement that may be typical of a positively driven device. 
     Accordingly, the present invention comprises: 
     a method of improving flow rate uniformity of material flowing to a spinner spreader with controlled capacity for impeding flow and a concomitant increased ease of passing debris which might otherwise interfere with uniformity of flow of the material, comprising the steps of: 
     providing a conveyor for transporting material outwardly from a storage container which is carried upon a wheeled vehicle; 
     conveying material by the conveyor; 
     providing a spinner, below the conveyor, configured for distributing the material after the material falls off an end of the conveyor; 
     allowing the material to drop from the conveyor onto the spinner where it is distributed; 
     providing a pivoting vibrator assembly, disposed at least in part above portions of the conveyor and in contact with the material, while the material is being conveyed by the conveyor; 
     causing the pivoting vibrator assembly to vibrate, and thereby increase a flow consistency of the material on to the spinner; 
     configuring the pivoting vibrator assembly for and allowing the pivoting vibrator assembly to automatically pivot upwardly, as a result of a change in matter coming in contact with the pivoting vibrator assembly, and thereby increasing a gap through which the matter can drop below the conveyor. 
     An apparatus for improving uniformity in spreading of material by improving uniformity of flow of matter off an end of a conveyor exiting from a material storage bin on a wheeled vehicle, comprising: 
     a conveyor sized, located and configured to move dry bulk material from a material storage bin on a wheeled vehicle; 
     a spinner disposed below the conveyor and configured to spread material falling from an end of the conveyor; 
     a mounting structure, disposed above the conveyor; 
     a pivoting vibrator assembly pivotally coupled to the mounting structure and gravitationally biased with respect to the mounting structure, so as to allow gravity to swing the pivoting vibrator assembly downwardly toward the conveyor and into contact with material being conveyed on the conveyor, and upwardly away from the conveyor when increased forces upon the pivoting vibrator assembly occur, which increased forces arise from impact between matter being conveyed by the conveyor and the pivoting vibrator assembly; and 
     wherein the pivoting vibrator assembly comprises:
         an array of a plurality of elongated rigid cutting blades; and   a vibrator coupled to and vibrating the array.       

     An apparatus for improving uniformity in spreading of material by improving uniformity of flow of matter off an end of a conveyor exiting from a material storage bin on a wheeled vehicle, comprising: 
     a conveyor sized and located to move particulate matter from a bin on a vehicle; 
     a rotating member disposed below the conveyor and configured to spread particulate matter falling from an end of the conveyor; 
     a mounting structure, disposed above the conveyor; 
     a pivoting assembly coupled to the mounting structure and biased, so as to allow the pivoting assembly to fall downwardly toward the conveyor and into contact with material being conveyed by the conveyor, and upwardly away from the conveyor when increased forces upon the pivoting assembly occur, which increased forces arise from impact between matter being conveyed by the conveyor and the pivoting assembly; and 
     wherein the pivoting assembly comprises:
         an array of a plurality of elongated members; and   a vibrator coupled to and vibrating the array.       

    
    
     
       BRIEF DESCRIPTIONS OF DRAWINGS 
         FIG. 1  shows a cross-sectional view of a prior art system for distributing matter. 
         FIGS. 2A through 2D  show sequenced cross-section views of the conveyor discharge area of the prior art system of  FIG. 1  with inconsistent material flow. 
         FIG. 3  shows a cross-sectional view taken on line  3 - 3  of  FIG. 4  with the pivoting vibrator assembly in a deployed configuration, where the dashed lines refer to portions of the blade  150  which would otherwise be concealed inside the material. 
         FIG. 4  is a perspective view of a portion of the present invention, including portions of the prior art system of  FIG. 1  with a conveyor discharge area with an embodiment of the present invention attached. 
         FIG. 5  is a detailed perspective view of the encircled portion of  FIG. 4 . 
         FIG. 6  is an alternate view of  FIG. 3  except for the pivoting vibrator assembly is in a stowed configuration. 
     
    
    
     DETAILED DESCRIPTION 
     Now referring to the drawings wherein like numerals refer to like matter throughout, and more particularly,  FIG. 1  is a cross-sectional view of a prior discharge area of a material bin  1 , conveyor end  2 , conveyor  3 , metered material  4 , and metering gate  5  shown in an at rest state as if the conveyor  3  had ceased movement. When the metered material  4  on the conveyor  3  is a truly free-flowing material, it may exhibit a shallow angle of repose  6 . As the conveyor  3  begins to move, free-flowing metered material  4  will fall off the conveyor end  2  with a nearly constant angle of repose  6 , and the flow of material will be a continuous and constant rate. Below conveyor end  2  is a chute  7  which guides material to a one or more rotating spinner disks  8 . 
       FIGS. 2A through 2D  are cross-sectioned sequence views of a metered material  4  that is not completely free flowing. Referring specifically to  FIG. 2A , the angle of repose  61  is determined by several factors, including, but not limited to friction, cohesion, shapes of particles, and density of the material  41 . In  FIG. 2B , as the base of the metered material stream drops from rotating conveyor end  2 , the friction, cohesion, and shapes of particles holds the material  41  together, and the apparent angle of repose  62  becomes larger. As shown in  FIG. 2C , the angle of repose  63  can grow larger until the leading surface  9  of the metered material  41  is nearly vertical.  FIG. 2C  shows the system immediately before the moment when the weight of material overcomes the forces holding the material  41  together. In  FIG. 2D , it can be seen that a portion  10  of the metered material  41  will dislodge and fall together as a large mass in the form of a slump, block, or avalanche, leaving the material with an angle of repose  61 . The process then repeats as shown from  FIGS. 2A through 2D , and the result is a discontinuous or inconsistent flow of material. A spinner  8  ( FIG. 1 ) or any other device positioned below the conveyor end  2  needing a consistent flow might not be able to perform its intended task. 
       FIGS. 3 ,  4  and  5  are, respectively, a cross-section view, a perspective view, and an enlarged perspective view of the present invention. 
     Now referring to  FIGS. 3 ,  4  and  5 , there is shown the anti-slab mechanism  300  of the present invention which comprises a pivoting vibrator assembly  100 , a mounting structure assembly  200  and a latching mechanism  400 . 
     Pivoting vibrator assembly  100  comprises a vibrator  110 , which may be an electrical vibrator configured to operate at 1800 cycles per minute or even up to 4000 cycles per minute; the vibrator  110  may be attached to a mounting plate  120  and transverse member  130 . The energy from the vibrator  110  is transferred through the mounting plate  120  to the transverse member  130  into a number of shaped blades  140  &amp;  150  that are placed across the path of, and generally aligned with, the metered material  41  flow. 
     Outside blades  150  pivot so as to keep the cutting inner blades  140  in contact with the metered material  41  starting at a predetermined angle  170 . If no material  41  is present, the outer blades  150  include a preferably non-abrasive flat surface  180  that rides on the conveyor  3  and prevents the cutting inner blades  140  from damaging the conveyor  3 . 
     The pivots  160  about which the outside blades  150  pivot, include an isolator bushing  190  that prevents vibration and noise generation in the mounting structure  200 . 
     The vibrator  110  is positioned to create an orbital motion perpendicular to the pivots  160 . Vibrator  110  may be orbital and electric, hydraulic or pneumatic. The vibratory motion causes the blades  140  &amp;  150  to both slice into the flow of metered material  41  and agitate the volume of material near the surface at the starting angle  170 . This motion frees particles from locking friction and cohesion to create a material flow that is nearly free flowing. 
     Furthermore, the vibrator  110  is positioned so most of the energy is directed at the base of metered material  41  near the conveyor end  2 . The portion of inner blades  140  farthest from the vibrator  110  are not retained and are free to vibrate along the length of the blade to free the material. The side surfaces  141  and  151  of the inner blades  140  and outer blades  150 , respectively provide large contact action area to laterally interact with the material  41 , thereby facilitating increased flow rate uniformity. The blades  140  and  150  are also stiff in the direction of material flow to cut into the surface of the material flow or provide strength required to pivot the pivoting vibrator assembly  100  away from large objects in the metered material  41  flow. 
     The shape and angle of the blades  140  and  150  are such that they agitate and create free flow for any setting of the meter gate  5  and metered material  41  depth on the conveyor  3 . Furthermore, the vibrator  110  frequency setting, location, blade shapes, blade angles, pivots  160 , and overall mass of the pivoting vibrator assembly  100  allow penetration into the upper layer of material an optimal amount. This optimal penetration or tuned working depth of the blades keeps the material flowing freely without impeding large material flows. In alternate embodiments, there may be means for biasing the flat surfaces  180  to the conveyor  3  which may include increased mass, via adding additional weights, or compressed springs or other suitable substitutes. 
     As the pivoting vibrator assembly  100  is mounted pivotably at the outer blades  150  end and can move out of the way of any solid foreign object that could be in the metered material  41  stream, likewise the pivoting vibrator assembly  100  can be pivoted completely out of the material path for storage when it is not needed as shown in  FIG. 6 . 
     The storage of the pivoting vibrator assembly  100  is accomplished by pivoting it away from the conveyor end  2  into the latching mechanism  400  which comprises an escapement  210  that can be locked into place. In the preferred embodiment of the invention, a hillside divider  220 , which is often needed for free-flowing material, acts to lock the pivoting vibrator assembly  100  in the storage position. Pivoting vibrator assembly  100  also provides support for the hillside divider  220 .

Summary:
An anti-slabbing device pivotally coupled above a material conveyor and configured to drop down onto material conveyed and further configured so as to vibrate the leading edge of the material as it reaches the end of the conveyor to create a more consistent flow of material from the end of the conveyor down onto a spinner for distributing the material.