Abstract:
A spreader for distributing a material on a surface. In certain embodiments, the spreader may include a disk rotatable about an axis and having an upper surface extending substantially radially from the axis. A driver may operably connect to the disk to provide rotation about the axis. A paddle may secure to the upper surface of the disk and rotate therewith. The paddle may be aligned to rotationally engage particulate material directed thereto and generate a centrifugal acceleration therein. A controller may limit the centrifugal release of the particulate material from the apparatus.

Description:
RELATED APPLICATIONS 
   This application claims priority to U.S. Provisional Patent Application Ser. No. 60/337,701, filed on Nov. 7, 2001, entitled COMBINATION DROP AND BROADCAST SPREADER FOR SPREADING GRANULAR MATERIAL and U.S. Provisional Patent Application Ser. No. 60/340,748, filed on Nov. 30, 2001, entitled SAFETY SHIELD FOR ROTATING SPINNER. 

   BACKGROUND 
   1. The Field of the Invention 
   This invention relates to transporting and distributing particulate material and, more particularly, to novel systems and methods for drop and broadcast spreading of materials used in turf care. 
   2. The Background Art 
   Agrarians have always been interested in efficiently managing their land. Common land management tasks include spreading substances such as seed, water, fertilizer, and the like. The quality of the land and its produce often depend on the even distribution of these vital substances. Uneven distributions result in waste and may even hinder or halt the progress of the desired vegetation. For these reasons, agrarians have developed various spreaders to rapidly and evenly distribute seed, fertilizer, water, sand, other soil amendments, and the like, thus, providing improved or ideal conditions for the vegetation of their choice. 
   In modern times, spreaders have been applied to the treatment of lawns and turf, particularly for parks, athletic fields, golf courses, and the like. Modern spreaders are also used for other purposes such as distributing cinders, salt, sand or other de-icing materials on winter roads. Broadcast spreaders and drop spreaders are the most common varieties of spreaders. A broadcast spreader typically includes one or more rotating spinners. The rotation of the spinner generates a centrifugal acceleration in the material deposited thereon, resulting in an arcuate distribution upon tangential release. In larger capacity models, broadcast spreaders often rely on a conveyor to deliver material to the spinners. Broadcast spreaders are suited for applications involving smaller amounts of material spread over large areas. For example, broadcast spreaders are often helpful in spreading fertilizer, pesticide, seed, top-dressing material, and the like. 
   Drop spreaders typically distribute a material by simply dropping it through one or more apertures directly onto a ground surface. On larger capacity models, a conveyor may assist in the removal of the material from a hopper. A conveyor may also assist in the metering out of the material. Drop spreaders are well suited for spreading larger amounts of material over a limited width. Typically, drop spreaders only distribute the material across a width roughly equivalent to the width of the spreader itself. Drop spreaders are often used as top dressers to apply a layer of sand, topsoil, gravel, or the like. 
   Recent advances in turf care, particularly golf green care, suggest that lighter more frequent applications of selected materials maximize turf quality. Broadcast spreaders are particularly well suited for such light applications if they can provide uniformity. However, there are still many applications that require a heavier, more controlled application of material. Heavy applications often require a drop spreader. As a result, combination drop and broadcast spreaders have been introduced. 
   While an improvement, combination spreaders are still susceptible to many of the weaknesses associated with the individual drop and broadcast spreading machines. Additionally, combination spreaders encounter difficulty in handling the wide variety of materials that are distributed by both drop and broadcast spreading devices. 
   Top-dressing materials used on sports turf and golf fairways and greens typically have some combination of sand, silt, clay, peat, lime, gypsum, and/or soil. When the moisture content is high, top-dressing material becomes cohesive and resistant to flow. As a result, it becomes more difficult to remove the material from the hopper and provide a consistent metering. Consequently, conveyors having chevron, herringbone, or other raised patterns on the surface have been introduce to assist in drawing the top-dressing material from the hopper though a metering port. 
   Conveyors with raised patterns cause two problems. First, the wet mixture clings to the conveyor between the raised portions of the surface pattern. Instead of falling off the conveyor as desired, the top-dressing material often sticks to the carrier. When top-dressing material does fall off the conveyor, it often does so in uneven clumps. Removal of the top-dressing material from conveyors with raised patterns has proven to be a difficult challenge. A simple scraper does not work well with raised patterns. Other more effective removal devices are complicated and inhibit the addition of other distributing attachments. 
   A second problem occurs when all of the recesses between the raised patterns become filled with top-dressing material. In effect, a conveyor with recesses filled acts just like a smooth conveyor. As a result, the device again is faced with the challenge of drawing the moist top-dressing material from the hopper with consistent metering. 
   Other challenges of combination spreaders must be addressed regardless of the moisture content of the material to be distributed. For example, maintaining a desired distribution pattern of equal density is another common challenge. Much effort has been invested in producing an even lateral (i.e. side to side with respect to the direction of travel) distribution. For example, if a broadcast type spreader is used to apply top-dressing material to a golf green, any uneven distribution will soon be noticeable. Moreover, as uneven applications accumulate, the problem is exacerbated and the result must be corrected with considerable difficulty. 
   Another challenge in combination spreader design relates to loading heights. For ease of loading, it is advantageous to minimize the loading height. However, low profile spreaders have difficulty maintaining a sufficient trailing clearance. The trailing clearance is the spacing from the tires to the lowest part of the spreader behind the tires. A sufficient trailing clearance is necessary to avoid damaging turf, or the spreader itself, as the spreader is moved on and off of elevated greens and through undulations. 
   Trailing clearance and other operational constraints are often at odds or balanced with one another with difficulty. For example, converting a drop spreader to a broadcast spreader often entails the addition of a funnel. Typically, twin spinners are employed on a broadcast spreader. Often the spinners are placed adjacent one another. Funnel height restriction, imposed by overall height and trailing clearance considerations, often results in funnel angles so shallow that the wet, cohesive material sticks to the funnel walls stopping further flow. 
   Additionally, with typical spreaders, due to the larger number of variables, it is difficult to know how much material is actually being distributed at any given time. For example, a user may be faced with adjusting spinner speed, spinner angle with respect to the ground, metering-port dimensions, conveyor speed, and spreader speed to achieve a desired application. The characteristics of the material to be distributed must also be considered. These variables are too numerous for a user to take into consideration when trying to generate a desired application of material. 
   Safety considerations also present challenges to spreader design. Powered broadcast spreaders, for example, use rotating paddles to throw material in a wide pattern. Rotating paddles cannot be completely covered or protected without adversely affecting the function of the broadcast spreader. Rotating paddles are typically shielded on a portion of their periphery to control the spread pattern and direct the stream of the distributed material. If a user were to inadvertently put a foreign object such as a hand or foot in the path of a rotating paddle, the paddle would shear the foreign object as it passes by the edge of the shielding. On typical powered broadcast spreaders the shear point, where the paddle passes the edge of the shielding, is exposed and readily accessible to the user. 
   Various solutions have been proposed to lessen the danger of the exposed shear point. However, these proposed solutions do not remove the shear point. Rather, they act to merely impede access to the shear point. With such measures, if a hand or finger did inadvertently enter the path of the spinner at the shear point, significant damage would still occur. Meanwhile, obstructions to hands are often obstructions to distribution of the granular material. 
   The foregoing challenges and design considerations, as well as others, are addressed by the present invention. 
   BRIEF SUMMARY OF THE INVENTION 
   Consistent with the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a method and apparatus are disclosed in one embodiment of the present invention as including a spreader having longitudinal, lateral, and transverse directions for distributing a material laterally and longitudinally on a surface during longitudinal travel of the spreader. 
   The spreader may include a hopper having a wall to contain a quantity of material. An aperture or hopper exit may be located proximate the bottom of the hopper. In one embodiment, the hopper exit may be located transversely lower than substantially all of the hopper to facilitate removal of the material from the hopper. A conveyor comprising a carrier powered by a driver may urge material passing through the hopper exit toward a metering port providing a consistent output of metered material. 
   A compression plate secured proximate the hopper exit may extend therefrom toward the carrier, forming a passage terminating at the metering port. The compression plate may be positioned at an angle with respect to the carrier. The angle may be selected to urge the material toward the carrier sufficiently to frictionally engage the material with the carrier and draw the material, metered, through the metering port. In selected embodiments, the compression plate comprises a material selected to provide with the material a lower effective coefficient of friction than the effective coefficient of friction between the material and the carrier. 
   A carrier in accordance with the present invention may be any suitable mechanism. For example, a carrier may be formed of a chain, a rack, a belt, a link belt, decks, and/or platens. In one embodiment, the carrier is formed as a continuous belt supported on rollers. 
   The outer surface of the carrier may engage the material as it is drawn past the compression plate and through the metering port. In certain embodiments, the outer surface of the carrier is substantially smooth to facilitate removal of all material adhering thereto. In selected embodiments, the smooth outer surface of the carrier supports the use of a scraper positioned to scrape the carrier and promote a complete and continuous deposition of all metered material onto the ground surface. 
   Various distributors may be attached to a spreader in accordance with the present invention. Suitable distributors may include spinners and roller brushes. Moreover, in selected embodiments, a distributor may be omitted, permitting the metered material to fall directly from the carrier to the ground surface as a “drop spreader” distribution. 
   A distributor with spinners in accordance with the present invention may have at least one funnel delivering material from the carrier to at least one spinner. The spinner may rotate and propel the material out onto the ground surface. In selected embodiments, a distributor may comprise two funnels delivering material to two rotating spinners. 
   Each spinner may define axial and radial directions orthogonal to one another. A disk may rotate about an axis extending in the axial direction. The upper surface of the disk may extend in the radial direction to receive the material thereon. A driver may provide rotation of the disk about the axis. One or more paddles may be secured to the upper surface of the disk to extend in the axial direction therefrom and rotate therewith. The one or more paddles may be positioned to rotationally engage the material deposited on the upper surface of the disk and generate a centrifugal acceleration therein. A shroud may provide a gradually decreasing barrier to the centrifugal release of the material from the disk, thus, generating a more even distribution of the material on the ground surface. 
   In certain embodiments, the orientation of the paddles with respect to the disk may be selected to provide an optimum distribution for a particular material. For example, one or more paddles may be secured by an adjustment mechanism to the upper surface of the disk. The adjustment mechanism may provide multiple angles, with respect to a radius of a disk, at which the paddle may be substantially rigidly secured to the disk. Applicants have discovered that as few as two paddles may suffice, and more paddles may be used. 
   Various guards may be incorporated to remove, or substantially reduce the risk of, pinch points between the rotating paddles and the stationary shroud. For example, a flexible guard may be secured to the shroud at the pinch point. The flexible guard may deflect when a foreign object is pushed thereagainst by a paddle. In certain embodiments, the flexible guard may be positioned to generate a restoring force urging the flexible guard to return to a natural position. The natural position may be manipulated so that the restoring force, once the flexible guard is deflected, may have the effect of urging the foreign object away from the pinch point. 
   A roller brush distributor in accordance with the present invention may comprise a roller brush rotating about an axis extending in the lateral direction. The roller brush may be positioned to contact the metered material resting on the carrier so as to propel the metered material downward toward the ground surface. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects and features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings in which: 
       FIG. 1  is a perspective view of a combination drop and broadcast spreader in accordance with the present invention with the distributor attachment in place; 
       FIG. 2  is a perspective, partial cut-away of a combination drop and broadcast spreader in accordance with the present invention without the distributor attachment in place; 
       FIG. 3  is a partial, side, cut-away view of a hopper exit and substantially smooth carrier illustrating the bridging effect that may occur in the material to be distributed; 
       FIG. 4  is a partial, side, cut-away view of a hopper exit and carrier having a raised pattern illustrating clumping and filling of the recesses in the raised pattern by the material to be distributed; 
       FIG. 5  is a partial, side, cut-away view of a hopper exit, compression plate, and substantially smooth carrier in accordance with the present invention illustrating metering of a material to be distributed; 
       FIG. 6  is a partial, side, cut-away view of a hopper exit, compression plate, and substantially smooth carrier in accordance with the present invention illustrating metering of a material to be distributed; 
       FIG. 7  is a side, cut-away view of a combination drop and broadcast spreader in accordance with the present invention illustrating metering of a material to be distributed; 
       FIG. 8  is a perspective view of a distributor attachment in accordance with the present invention; 
       FIG. 9  is a perspective, cut-away view of a spinner in accordance with the present invention; 
       FIG. 10  is a top view of two spinners and the flight paths and a possible distribution curve generated thereby; 
       FIG. 11  is a partial, perspective view of an embodiment of a spinner and abrupt release edge capable of generating the distribution curve of  FIG. 10 ; 
       FIG. 12  is a top view of two spinners and the flight paths and a possible distribution curve generated thereby in accordance with the present invention; 
       FIG. 13  is a partial, perspective view of an embodiment of a spinner and gradual release edge capable of generating the distribution curve of  FIG. 12  in accordance with the present invention; 
       FIG. 14  is a partial, perspective view of an alternate embodiment of a gradual release edge capable of generating the distribution curve of  FIG. 12  in accordance with the present invention; 
       FIG. 15  is a partial, perspective view of an alternate embodiment of a gradual release edge capable of generating the distribution curve of  FIG. 12  in accordance with the present invention; 
       FIG. 16  is a partial, perspective view of an alternate embodiment of a gradual release edge capable of generating the distribution curve of  FIG. 12  in accordance with the present invention; 
       FIG. 17  is a partial, perspective view of an alternate embodiment of a gradual release edge capable of generating the distribution curve of  FIG. 12  in accordance with the present invention; 
       FIG. 18  is a partial, perspective view of an embodiment of a spinner and periodic release edge capable of generating the distribution curve of  FIG. 12  in accordance with the present invention; 
       FIG. 19  is a top view of a disk with adjustable paddles in accordance with the present invention, illustrated with the paddles adjusted to a paddle angle of zero; 
       FIG. 20  is a top view of a disk with adjustable paddles and metered material in accordance with the present invention, illustrated with the paddles adjusted to a paddle angle greater than zero; 
       FIG. 21  is a top, cut-away view of a spinner illustrating a pinch point between a paddle and shroud; 
       FIG. 22  is a perspective view of a spinner with a guard extending therefrom in a natural position in accordance with the present invention; 
       FIG. 23  is a perspective view of the spinner of  FIG. 22  with the guard deflected to the activated position in accordance with the present invention; 
       FIG. 24  is a top, cut-away view of a spinner illustrating a spacing to limit accessibility to the pinch point between a paddle and shroud in accordance with the present invention; 
       FIG. 25  is a top, cut-away view of the spinner of  FIG. 22  illustrating the reaction of the guard to the pinching of a foreign object in the pinch point in accordance with the present invention; 
       FIG. 26  is a side, cut-away view of a spreader employing a roller brush distributor in accordance with the present invention; 
       FIG. 27  is a schematic of an embodiment of a hydraulic power system for powering a combination drop and broadcast spreader in accordance with the present invention; and 
       FIG. 28  is a chart plotting application rate as a function of carrier speed, as controlled by various valve settings, and spreader speed in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the system and method of the present invention, as represented in  FIGS. 1 through 28 , is not intended to limit the scope of the invention, as claimed, but is merely representative of certain embodiments of apparatus and methods in accordance with the invention. 
   The embodiments of systems in accordance with the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. Those of ordinary skill in the art will, of course, appreciate that various modifications may easily be made without departing from the essential characteristics of the invention 
   Referring to  FIG. 1 , in describing a spreader  10  in accordance with the present invention, it may be advantageous to first define longitudinal  11   a , lateral  11   b , and transverse  11   c  directions positioned to be substantially mutually orthogonal. In general, the longitudinal direction  11   a  will be aligned with the horizontal direction of travel of the spreader  10  in operation. The lateral direction  11   b  will extend from side to side. By default, the transverse direction  11   c  will then be aligned with a direction close to vertical. All directions are with respect to the spreader  10 , since ground may not be level. 
   The structures of a spreader  10  typically accomplish three basic functions. First, the material is stored. Second, the material is metered or parceled. Finally, the metered material is applied to a selected ground surface area. A spreader  10  in accordance with the present invention may be divided into componentry according to these three functions. For example, the storing may be accomplished by a hopper  12 . The metering may be accomplished by a conveyor  14 . And finally, the application to the ground surface may be accomplished by a distributor  16 . 
   A hopper  12  in accordance with the present invention may have any suitable shape (e.g. round, rectangular, trapezoidal, etc.) for containing the material  36 . In certain embodiments, a hopper  12  may include a front wall  18 , a rear wall  20 , a first side wall  22 , and a second side wall  24 . The walls  18 ,  20 ,  22 ,  24  may be arranged to form an open top  26  and an open bottom  28 . In general, the walls  18 ,  20 ,  22 ,  24  may be formed of any suitable material and be connected in any suitable manner. For example, in certain embodiments, the walls  18 ,  20 ,  22 ,  24  are made of a polymer molded as a single piece. In another embodiment, the walls  18 ,  20 ,  22 ,  24  are constructed of sheet metal secured together by fasteners  30 . Other suitable materials may include wood, reinforced polymer, and the like. Other suitable forming methods may include welding, snapping, glueing, and the like. 
   The walls  18 ,  20 ,  22 ,  24  may be formed to increase strength and rigidity while minimizing weight. For example, in one embodiment, sheet metal walls  18 ,  20 ,  22 ,  24  may have folds  32  bent therein to increase the section modulus. In other embodiments, ribs, corrugations, and the like may be employed. 
   Referring to  FIG. 2 , a spreader is illustrated without the distributor  16  attached. In selected embodiments in accordance with the present invention, the hopper  12  may be secured above the conveyor  14  to deposit material  36  thereon under the impetus of gravity. In certain embodiments, the conveyor  14  may be positioned below the hopper  12  to form the base to the hopper  12 . Thus, the hopper  12  may support a quantity of a material  36  in the longitudinal  11   a  and lateral  11   b  directions, while the conveyor  14  supports the material  36  in the transverse direction  11   c.    
   A conveyor  14  may include a carrier  34 . A carrier  34  in accordance with the present invention may be any suitable mechanism. For example, a carrier  34  may be formed of a chain, a rack, a belt, a link belt, decks, and/or platens. In selected embodiments, a carrier  34  may circulate around and be supported by a front roller  38  rotating about a front axis  40  and a rear roller  42  rotating about a rear axis  44 . For convenience in discussion, in certain embodiments, a carrier  34  may be defined to have an upper half  46 , a lower half  48 , an outer surface  50 , and an inner surface  52 . 
   If a more flexible carrier  34  is used, a carrier support  54  may support the upper half  46  of the carrier  34  to resist sagging due to the weight of the material  36  resting thereabove. The front and rear rollers  38 ,  42  may be supported in their respective positions by first and second rails  56 ,  58  extending in the longitudinal direction  11   a . Cross members  60  and other structural elements may be added as needed to provide sufficient rigidity and strength. U.S. Pat. No. 6,202,944 B1 (the &#39;944 patent) issued to McCrory and entitled MATERIAL SPREADING APPARATUS is incorporated herein by reference. The &#39;944 patent describes various belt and belt support configurations that may be applied to the present invention. 
   In general, a spreader  10  in accordance with the present invention may be propelled, towed, or otherwise moved by any suitable motivator or motive means. Thus, any structure necessary to provide a suitable interface with the motivator is considered to be within the scope of the present invention. For example, various apertures  62  and extensions  64  and other structures may be included as part of a spreader  10  in accordance with the present invention. The apertures  62  and extensions  64  may support securement of wheels, towing hitches, and the like. In other embodiments, the apertures  62  and extensions  64  support securement of the spreader  10  onto the bed of a vehicle to create a self-propelled spreader  10 . 
   A driver  66  may be provided to generate motion of the carrier  34 . In selected embodiments, such as those using a conveyor belt  34 , the driver  66  may engage the rear roller  42  and generate a desired direction of rotation  68 . In one embodiment, the direction of rotation  68  is selected to pull material  36  resting on the outer surface  50  of the upper half of the of the carrier  34  from a front end  70  to a rear end  72  of the spreader  10 . Thus, when the driver  66  is activated, the material  36  may be pulled from the hopper  12  through a hopper exit  74  formed in the rear wall  20  of the hopper  12 . In another embodiment, the material  36  may leave the hopper  12  under the impetus of gravity and be deposited on the carrier  34 . 
   A hopper exit  74  in accordance with the present invention may have an exit height  76  and an exit width  78 . The exit height  76  and width  78  may be selected to best accommodate the various compositions of the material  36  to pass therethrough. In selected embodiments, the exit width  78  roughly corresponds to the span of the carrier  34  in the lateral direction  11   b.    
   In certain embodiments, a compression plate  80  may be secured proximate the hopper exit  74 . In one embodiment, a compression plate  80  may secure to the rear wall  20  of the hopper  12  and extend towards the rear end  72  of the spreader  10 . In selected embodiments, the rearward-most end of the compression plate  80  may be held in a desired location by a brace  82  forming a substantially rigid triangular cross section between itself, the rear wall  20 , and the compression plate  80 . Fasteners  84  may secure the compression plate  80 , brace  82 , and rear wall  20  respectively to one another in a desired location. 
   In selected embodiments, the compression plate  80  may slope downward in the transverse direction  11   c  as it extends rearwardly in the longitudinal direction  11   a . In another embodiment, the compression plate  80  may simply slope toward the carrier  34 , whatever direction that may be. The slope may be defined and quantified by a compression angle  86 . The magnitude of the compression angle  86  may inversely correspond to a height of a metering port  88 . That is, if the compression angle  86  is zero, then the height of the metering port  88  is the same as the height  76  of the hopper exit  74 . If, on the other hand, if the compression angle  86  is ten degrees, then the metering port  88  will have a height less than the height  76  of the hopper exit  74 . Thus, the compression plate  80  may act to compress the material  36  traveling on the carrier  34  before it can leave the metering port  88  and fall from the carrier  34  at the discharge pont  90  or dumping point  90 . In embodiments where the carrier  34  is a conveyor belt  34 , the dumping point  90  may be the point of belt inversion  90 . 
   Referring to  FIG. 3 , any suitable material  36  may be a material  36  to be distributed in accordance with the present invention. Suitable materials  36  may include sand, gravel, soil, salt, de-icing pellets, seed, fertilizer, top-dressing, and the like. Top-dressing materials  36  that are used on sports turf and golf fairways and greens typically include some combination of sand, silt, clay, peat, lime, gypsum and/or soil. 
   When the moisture content of some materials  36  is high, as is often the case, the material  36  becomes cohesive and resistant to flow. This cohesiveness may cause the material  36  to trap air, forming voids  92 , which may result in inconsistent metering. However, perhaps more significantly, this increase in cohesiveness greatly increases the shear modulus of the material  36 . As a result, the material  36  resists exiting the hopper. 
   Depending on the height  76  of the hopper exit  74 , the moisture induced cohesiveness may be sufficient to stop material  36  from exiting the hopper  12  entirely. Thus, the carrier  34  may advance  94  and retreat  96 , without transporting any material  36 . For example, in selected embodiments, where the hopper exit  74  also acts as the metering port, the hopper exit height  76  is relatively small. As a result, the cohesiveness may generate a bridging effect  98  which the weight  100  of the material  36  pressing down thereon is unable to collapse. Moreover, in embodiments where the carrier  34  aids in the removal of material  36  from the hopper  12 , the friction force  102  between the moving carrier  34  and the material  36  is also unable to overcome the cohesive bridging effect  98 . 
   Referring to  FIG. 4 , to increase the friction force  102  so that it may overcome the cohesive bridging effect  98 , cleats  104  may be incorporated as part of the outer surface  50  of the carrier  34 . However, depending on the consistency of the material  36  there may be significant disadvantages to the use of cleats  104 . For example, the cleats  104  typically do not remove voids  92  from the material  36 . Rather, the cleats  104  may even increase the occupancy of discontinuities  106  as the material  36  passed through the hopper exit  76 . Moreover, often the reliefs  108  between the cleats  104  collect material  36  and after a short period of time fill, thus, nullifying the effect of the cleats  104 . Due to the discontinuous nature of the outer surface  50  of the carrier  34 , cleaning out the reliefs  108  can become a significant problem. 
   Referring to  FIG. 5 , the cohesive bridging effect  98  weakens as the distance it must span increases. As a result, if the height  76  of the hopper exit  74  is sufficiently large, the bridging effect  98  will break down and cohesive material  36  may be drawn out of the hopper  12 . However, a large hopper exit  74  causes additional challenges in that it may be difficult to meter the material  36  exiting therethrough. A compression plate  80  in accordance with the present invention addresses both difficulties by providing a hopper exit  74  with a large exit height  76  and a closely controlled, precise metering port  88 . 
   For convenience of discussion, a compression zone  110  may be defined as the three dimensional volume bounded by the compression plate  80  and the upper half  46  of the carrier  34  in the transverse direction  11   c  and by the hopper exit  74  and the metering port  88  in the longitudinal direction  11   a . However, it is readily understood that in certain embodiments, the directions used in defining the compression zone  210  may differ. The height  76  of the hopper exit  74  may be sufficiently large to overcome the cohesive bridging effect  98  and permit the material  36  to flow out. In other embodiments, the sufficiently large hopper exit  74  permits the friction force  102  of the carrier  34  to draw the material  36  out of the hopper exit  74  and into the compression zone  110 . 
   Once inside the compression zone  110 , the mechanical characteristics of the material  36  largely determine the dynamics that follow. For example, a relatively compressible material  36  containing voids  92  will gradually be compressed by the ever decreasing area imposed thereon by the compression angle  86  of the compression plate  80  until it reaches the metering port  88 . As a result, the material  36  exits the metering port  80  as a substantially voidless, metered material  112 . Interstitial voids between particles in compact contact are not “voids” in this context. 
   It is well known that the friction force between adjacent objects is equal to the force pushing the objects against each other (the normal force) times a coefficient of friction based on characteristics of the two abutting surfaces of the objects. Thus, frictional forces can be increased by increasing the normal force or by increasing the coefficient of friction between the opposing surfaces. 
   For example, a wedge with the high end placed against a door is ineffective as a doorstop. The weight (normal force) forcing the wedge against the floor is insufficient to generate the frictional forces necessary to stop the door from swinging. However, when the small edge is placed under the door, the incline pushes upward on the door which in turn pushes right back. This return force is transferred through the wedge to the floor surface, effectively creating a very large normal force. This normal force, even when multiplied by the same coefficient of friction as before, now creates a frictional force that easily holds the door in place. These principles of physics apply equally well to the compression plate  80  of the present invention. 
   In certain embodiments, the frictional force  100  applied by the carrier  34  to the material  36  outside of the compression zone  110  is a product of the weight  100  of the material  36  and a corresponding coefficient of friction. However, as the material  36  enters the compression zone  110 , the compression plate  80  exerts a normal force  114  thereon. The component  116  of the normal force  114  acting in the transverse direction  11   c  adds with the weight of the material  36  to generate a much greater friction force  102  between the carrier  34  and the material  36 . Thus, as the compression (normal force  114 ) of the compression plate  80  increase and tries to stop the advance  94  of the material  36 , the frictional force  102  is likewise increased and, therefore, the material  36  keeps advancing  94  through the compression zone  110 . 
   The transverse component  116  of the normal force  114  is inversely related to the compression angle  86 . That is, the greater the compression angle  86 , the less the transverse component  116  and the greater a longitudinal component  117  of the normal force  114 . Thus, there is a value of the compression angle  86  at which point the compression plate  80  becomes more of a hindrance than a help. This value may vary depending on the characteristics of the material  36 . In general, the lower the shear modulus of the material  36 , the greater the value of the compression angle  86  may be. 
   An increase in the normal force  114  exerted by the compression plate  80  increases a parasitic frictional force  118  between the plate  80  and the material  36 . This parasitic frictional force  118  typically acts in opposition to the desired frictional force  102  between the carrier  34  and the material  36 . However, this parasitic frictional force  118  may be controlled through selecting a material for the compression plate  80  that has a relatively low coefficient of friction with the material  36  to be distributed. Suitable materials may include a polished metal, polymer, reinforced polymer, and the like. In one embodiment, the compression plate is molded from polyethylene. 
   Parasitic frictional forces  118  may also be reduced by selective positioning of the fasteners  84 . For example, the fasteners  84  may be countersunk bolts. In another embodiments, the fasteners  85  may be insert molded to permit one entire side of the compression plate  80  to be smooth and continuous. 
   Through the use of a compression plate  80  in accordance with the present invention, a carrier  34  having a substantially smooth outer surface  50  may transport and accurately meter even cohesive material  36 . As a result, a scraper  120  may be employed to simply and effectively scrape all metered material  112  from the carrier  34 . Thus, all the advantages of a substantially smooth carrier  34  may be enjoyed without the frictional limitations usually associated therewith. 
   Referring to  FIG. 6 , as mentioned hereinabove, once the material  36  enters the compression zone  110 , the mechanical characteristics of the material  36  largely determine the dynamics that follow. For comparatively incompressible materials  36 , the rate of exit from the metering port  88  is substantially equal to the rate of entrance into the compression zone  110 . That is, the compression zone  110  has a much larger entrance (hopper exit  74 ) than exit (metering port  88 ). Therefore, all material  36  that enters does not immediately progress to the metering port  88 . Instead, the compression zone  110  acts as an accumulator, collecting excess material  36  in a recirculation/stagnation zone  122 . 
   Whether the excess material  36  in the compression zone  110  is recirculating or stagnant depends on the characteristics of the material  36 . However, in both situations, the excess material  36  in the recirculation/stagnation zone  122  waits its turn to pass through the metering port  88 . In such a situation, the compression zone  110  may act as an accumulator actively forcing, by both gravity and the normal force  118  of the compression plate  80 , the excess material  36  waiting in the recirculation/stagnation zone  122  into voids in the outgoing material  36 . Thus, a substantially continuous, metered material  112  exits though the metering port  88 . 
   Referring to  FIGS. 1 ,  7 , and  8 , in certain embodiments, it may be desirable to have a detachable distributor  16 . Thus, the spreader  10  may act as both a drop spreader (without the distributor  16 ) and as a broadcast spreader (with the distributor  16 ). Likewise the broadcast spreader can be used alone. A detachable distributor  16  in accordance with the present invention may secure to the conveyor  14  (or any other suitable structure of the rest of the spreader apparatus  10 ). In selected embodiments, the distributor  16  secures to the conveyor  14  with an attachment engaging system  124 . 
   In one embodiment, an attachment engaging system  124  in accordance with the present invention may include pivots  126   a ,  126   b  secured to the rails  56 ,  58  of the conveyor  14 . Additional engagement mechanisms  128  may also be secured to the rails  56 ,  58 . In certain embodiments, additional support structures  130  may be incorporate to support, engage, or otherwise aid in securement of the detachable distributor  16 . 
   A distributor  16  in accordance with the present invention may have flanges  132   a ,  132   b  secured together by suitable cross members  134  as desired. The flanges  132   a ,  132   b  may have hooks  136   a ,  136   b  to engage the corresponding pivots  126   a ,  126   b . Thus, once the hooks  136   a ,  136   b  engage the corresponding pivots  126   a ,  126   b , the distributor  16  may be pivoted into proper alignment with the rest of the spreader apparatus  10 . Flanges  132   a ,  132   b  may be formed with additional structures  138  corresponding to, and providing engagement with, the additional engagement mechanisms  128  to create a stable securement. 
   Referring to  FIGS. 7 and 8 , in certain embodiments, a distributor  16  may include a funnel  140  to direct metered material  112  to a spinner  142 . The spinner  142  may also operate alone without the full metering system. Although material  112  may be unmetered, the term metered material  112  shall include herein all material  112  distributed when appropriate, such as when broadcast without being exactly metered. The spinner  142  may then propel the metered material  112  out over the ground surface  144 . A funnel  140  in accordance with the present invention may have any suitable shape. For example, in selected embodiments, a distributor  16  may include more than one funnel  140  delivering metered material  112  to multiple spinners  142 . In one embodiment, two symmetrical funnels  140   a ,  140   b  are formed as a single unit to simultaneously deliver metered material  112  to two spinners  142   a ,  142   b.    
   A funnel  140  in accordance with the present invention may be formed of any suitable material. For example, a funnel  140  may be formed of a wood, metal, metal alloy, polymer, reinforced polymer, and the like. Factors that may be considered in selecting the material may be strength, durability, ease of manufacture, coefficient of friction with the metered material  112 , and the like. 
   A funnel  140  may be formed in a manner compatible with the funnel material. In one embodiment, the funnel  140  may be formed as two symmetrical funnels  140   a ,  140   b  molded as a single unit from polyethylene. A shoulder  145  may be formed as part of the funnel  140  to support the funnel  140  on cross members  134  and the like. In certain embodiments, the funnel  140  may be directly bound to the support structure (flanges  132 , cross members  134 , and the like) of the distributor  16  in few locations, thus, permitting expansion and contraction due to thermal influences without warping, bending, cracking, and the like. 
   If desired, a scraper  120  may be incorporated as part of the distributor  16 . In one embodiment, a scraper  120  is secured to a cross member  134  by fasteners  146 , thus permitting the scraper to contact the carrier  34  after is has past the dumping point  90 . In certain embodiments, a funnel  140  in accordance with the present invention may be formed with a funnel angle  148  selected to promote sliding of the metered material  112  therethrough. In certain embodiments, the geometries of the funnels  140   a ,  140   b  may be select to minimize the funnel angle  148 . The funnel angle  148  may be minimized by spacing the spinners  142  a distance  149  selected to allow the four greatest funnel angles  148   a ,  148   b ,  148   c ,  148   d  to be substantially equal. 
   Spinners  142   a ,  142   b  in accordance with the present invention may be rotated by any suitable driver  150 . Suitable drivers  150  may include motors, engines, cranks, power takeoffs, and the like. Other suitable drivers may include gears, sprockets, pulleys, shafts, and other mechanisms receiving their motion from a distant motive source or torque generator. In one embodiment, the driver  150  is a hydraulic motor. 
   On occasion, it may be desirable to position the driver  150  above the spinner  142 . Such a placement may increase trailing clearance below the spinner  142 . This additional trailing clearance may be particularly helpful to avoid spinner  142  contact with the ground while negotiating short, steep declines. Similar to dragging a car&#39;s rear bumper when traversing a deep gutter, contact between the spinner  142  and the ground is typically undesirable and may result in damage to either the ground, the spinner, or both. With a top-mounted driver  150 , it may be desirable to form a clearance space  152  in a nearby funnel  140 . 
   In selected embodiments, a mount  154  may secure the driver  150  to a top plate  156  of the spinner  142 . Any suitable engagement, between the driver  150  and spinner  142  may suffice. If desired, fasteners  158  of any suitable type (e.g. bolts, rivets, welds, etc.) may be employed. 
   In certain embodiments, a spinner  142  in accordance with the present invention, may include a disk  160  rotating about a disk axis  162 . Any suitable or beneficial alignment of the disk axis  162  may be utilized. In one embodiment, the disk axis  162  is aligned substantially with the transverse axis  11   c.    
   Paddles  164  may be secured to the disk  160  to assist in propelling the metered material  112  therefrom. Paddles  164  may be formed with any suitable cross section or shape. The cross section or shape may be selected to assist the spinner  142  in engaging and propelling the metered material  112 . 
   The disks  160 , paddles  164 , and componentry of the spinners  142  in general may be formed of any suitable material. Suitable materials may include a wood, metal, metal alloy, polymer, reinforced polymer, elastomer, combination thereof, and the like. Characteristics that may be taken into account when selecting component material may include strength, durability, abrasion resistance, frictional qualities, impact resistance, formability, cost, and the like. In one embodiment, the disk  160  and paddles  164  are formed of a metal. 
   Paddles  164  may be secured to the disk  160  in any suitable manner. For example, the paddles  164  may be welded, glued, bolted, snapped, slotted, pinned, wedged, keyed, or otherwise secured to the disk  160 . In certain embodiments, the disk  160  and paddles  164  may be formed as an integral unit (i.e. molded or machined from a single piece of stock). In one embodiment, the paddles  164  are secured to the disk  160  by fasteners  166 . A base  168  may be formed on the paddles  160  to assist the fasteners  166  in securing the paddles  164  to the disk  160 . In certain embodiments, the angles and locations of the paddles  164  on the disk are adjustable to control distribution. Any suitable number of paddles  164  may be secured to a disk  160 . The number of paddles  164  may be selected to promote a desired distributional pattern. In one embodiment, excellent and unexpected results were obtained when only two paddles  164  were secured to the disk  160 . Broad, even distribution was obtained. 
   A top plate  156  in accordance with the present invention may extend over the disk  160  and paddles  164  to limit the directions in which the metered material  112  may be released from the disk  160 . Moreover, the top plate  156  may prevent inadvertent insertion of a foreign object into the rotating spinner  142 . If desired, a bottom plate  170  may provide an additional guard and protection for the spinner  142 . 
   In selected embodiments, a shroud  172  may form a barrier surrounding a portion of the disk  160 , thus, limiting release of the metered material  112  (e.g. metered, fed, grossly metered, delivered, etc.) to a desired location called the release edge  174 . When the metered material  112  rotating on the disk  160  reaches the release edge, the outermost particles of the metered material  112  begin to exit the spinner  142  at their current tangent location and with a corresponding tangential velocity. The location of the release edge depends on the direction of rotation  176  of the disk  160 . If the disk  160  were to rotate opposite to the direction of rotation  176 , then the other end of the shroud  172  would become the release edge  174 . 
   In embodiments including more than one spinner  142 , intermediate regions  178  may connect the various spinners to increase strength, reduce vibration, and the like. For example, in one embodiment, a single top plate  156  extends over both spinners  142  while a single bottom plate  170  extends under both spinners  142 . In such a case, the portions of the top and bottom plates  156 ,  170  extending between the spinners  142  may be considered a strengthening intermediate region  178 . 
   Referring to  FIG. 9 , a disk  160  in accordance with the present invention may be secured to a shaft  182 . In one embodiment, the disk  160  is rigidly connected to a bushing  184  sized to receive the shaft  182 . If desired, the shaft  160  and bushing  184  may be keyed to prevent rotation therebetween. The shaft  182  may be rotatably held in place by an upper bearing  186  secured to the top plate  156  and by a lower bearing  188  secured to the bottom plate  170 . A coupler  190  may transmit rotation from the driver  150  to the shaft  182 . 
   Referring to  FIG. 10 , a spinner  142  may operate by applying a centrifugal acceleration to the metered material  112  deposited thereon by the funnel  140 . The centrifugal acceleration acts on the metered material  112  to force the material  112  in a radial direction  192  along the paddles  164  until further progress is stopped by the shroud  172  at the disk edge  194 . In such a position, the paddle  164  may be said to be “loaded.” 
   When a loaded paddle  164  rotates past a release edge  174 , the metered material  112  begins escaping the disk  160  under the impetus of the centrifugal acceleration. Each particle or clump of the metered material  112  escapes the disk  160  on a flight path  198 . Each flight path  198  is in effect a tangential flight path  198  extending away from the disk  160  along one of an infinite number of tangent lines. 
   It may be helpful to distinguish between the release and the escape of the metered material  112 . Release of a particle or clump of metered material  112  occurs when there is no longer a shroud barrier stopping travel in the radial direction  192  and preventing that particle or clump from flying off the rotating disk  160 . Typically, release occurs as a loaded paddle  164  passes a release edge  174 . Different particles and clumps of metered material  112  on a loaded paddle  164  may experience release at different times. 
   In contrast, escape is the moment when a particle or clump of the metered material  112  actually leaves the disk  160  and paddles  164 . For particles and clumps of metered material  112  on a loaded paddle  164  at the disk edge  194 , release and escape occur at roughly the same time. However, the escape of metered material  112  farther from the disk edge  194  may be delayed by several factors and occur sometime after release. To further illustrate, release is like the opening the starting gate granting a racehorse permission to start running, while escape is when the horse actual gets out of the chute. 
   Often, after release, the metered material  112  must wait in line behind other accumulated material  112  for its turn to escape. Metered material  112  nearer the disk edge  194  may escape first, followed by material  112  a little closer to the center of the disk (axis of rotation  162 ) until all the material  112  has escaped. Frictional forces between the metered material  112  and the disk  160  and paddles  164  may also affect the rate at which material  112  escapes, once it has been released. Other factors that may affect the rate at which material  112  is able to escape the disk  160  are the shear modulus of the material  112  as well as the angular velocity of the disk  160  and paddles  164 . At slower speeds, friction against the disk  160  may be more of a delay factor, slowing radial travel. 
   The particular tangential fight path  198  taken by a particle or clump of the metered material  112  may be mapped by drawing a vector, tangent to the disk  160  and originating from the location that the particle or clump escapes the forces of the disk  160  and paddles  164 . A release vector  199  may be defined as the direction and flight path  198  of a particle or clump of metered material  112  for which release and escape are substantially simultaneous. 
   A distribution curve  200  may be plotted to illustrate the distribution of the metered material  112  obtained by the spreader  10 . A vertical axis  202  may represent the quantity of metered material  112  delivered. A horizontal axis  204  may represent the lateral location relative to a line of substantial symmetry  206 . Often, the line of symmetry  206  corresponds to the path or direction of travel  208  of the spreader  10 . 
   The configuration of the release edge  174  has a significant and calculable effect on the release and escape of the metered material  112  as well as the distribution curve  200  that is generated. Thus, various categories of configurations for release edges  174  may be established. Three such categories are abrupt release edges  174 , gradual release edges  174 , and periodic release edges  174 . 
   Referring to  FIGS. 10 and 11 , the various categories of release edges  174  may be distinguished by the release vectors  199  that each respective release edge  174  generates. For example, the release vectors  199  of an abrupt release edge  174  all occupy a single, tangent plain  210 . Thus, all release vectors  199  for an abrupt release edge  174  point in the sample direction. The distribution curve illustrated in  FIG. 10  is typical of an abrupt release edge  174 . 
   Since the release vectors  199  of an abrupt release edge  174  point in the same direction, the majority of the particles and clumps of metered material  112  escape on flight paths  198  very near the tangent plane  210  containing the release vectors. Thus, a maximum  212  distribution, corresponding to predominant flight path (near tangent plane  210 ), forms in the distribution curve  200 . 
   It may be noted that not all escaping particles and clumps of the metered material  112  follow the path  198  indicated by the release vectors  199 . As mentioned hereinabove, waiting in line, friction forces, shear modulus, and the like may delay the escape of some particles and clumps until only more laterally directed flight paths  198  are available. However, due to the magnitude of the centrifugal acceleration, that delay is typically relatively short. The short delay results in bunching of the utilized flight paths  198  close to the release vectors  199 . As a result, very few particles and clumps of metered material  112  take the more laterally directed flight paths  198  to the lateral fringes  214   
   Referring to  FIGS. 12 and 13 , in gradual release edges  174 , no single tangent plane  210  can contain all of the release vectors  199 . Rather, each release vector  199  defines a distinct tangent plain  210 . Thus, only an infinite number of tangent plains  210   a ,  210   b , etc. can contain all of the release vectors  199  of a gradual release edge  174 . 
   The distribution curve  200  illustrated in  FIG. 12  is typical of a gradual release edge  174 . The distribution of release vectors  199  through a large number of tangent plains  210   a ,  210   b , etc. precludes the build-up of a large maximum  212 . More of the metered material  112  escapes on flight paths  198  directed to the lateral fringes  214 . Thus, a more even distribution curve  200  may be achieved. The edge fall-off  216  may be compensated by a slight overlap with the next, adjacent pass of the spreader  10 . 
   Referring to  FIGS. 13-17 , various configurations may form gradual release edges  174 . Any suitable configuration providing a gradual release of metered material  112  may be used for a gradual release edge  174 . For example, a gradual release edge  174  may be a slope  174 . The slope may extend from the top plate  156  to the bottom plate  170  or vice versa. The angle  216  of the slope  174  may correspond to the distribution desired. A more shallow angle  216  may be selected for a distribution extending more to the lateral fringes  214 . Other suitable gradual release configurations may include forked, curved, and perforated edges  174 . 
   Referring to  FIG. 18 , in certain embodiments, a periodic release edge  174  may be employed. A periodic release edge  174  may comprise several abrupt release edges  174  formed in series. Thus, the material  112  is released then contained, released then contained until the desired distribution curve  200  is achieved. The spacing between the various segments of the shroud  172  may be selected to permit some, but not all of the metered material  112  to escape. Thus, the periodic release edge  174  has the effect of stringing out the escape of metered material  112 . 
   Similar to the gradual release edge  174 , with a periodic release edge  174 , no single tangent plane  210  can contain all of the release vectors  199 . That is, while the release vectors  199  associated with a particular release edge  174   a  may occupy one plain  210   a , the release vectors  199  associated with another release edge  174   b  will occupy a distinct plain  210   b . Thus, the number of tangent plains  210   a ,  210   b , etc. may correspond to the number of the release edges  174   a ,  174   b , etc. placed in series. 
   In selected embodiments, release edges  174  in accordance with the present invention may be formed as inserts so that with minimal manipulation, release edges of various sizes, shapes, and configurations may be employed. For example, a spinner  142  may be formed to accept inserts in the form of abrupt, gradual, and periodic release edges  174 . In another embodiment, a spinner  142  may be configured to receive various shaped gradual release edges  174 . In one embodiment, a spinner  142  may receive sloped, gradual release edges  174  of varying slope angle  216  to accommodate a variety of metered materials  112 . In certain embodiments, a slope  174  may be adjustable to provide various slope angles  216  within a single device. Likewise, in certain embodiments, the circumferential location of the end of the shroud  172  may be selected or adjusted to vary the amount and distribution of material  112  dispensed. The actual length of the shroud  172  may be adjustable in a single device. 
   Referring to  FIGS. 19 and 20 , in certain embodiments, it may be advantageous to form paddles  164  that are secured to the disk  160  by an adjustment mechanism  218 . The adjustment mechanism  218  may support securement of the paddles  164  to the disk  160  at a paddle angle  220  arbitrarily selected with respect to a radius  222  of the disk  160  to meet a particular distribution performance. 
   The adjustment range of the adjustment mechanism  218  may include any paddle angle  220  having a beneficial affect on the spreading of the various types of metered materials  112 . In one embodiment, the adjustment mechanism supports a range of zero to twenty-five degrees of paddle angle  220 . Experimentation has shown that larger paddle angles  220  may be helpful in producing a desired distribution when spreading a relatively dry metered material  112 . Shallow paddle angles  220  have been shown effective for properly spreading metered materials  112  having a higher moisture content and more tendency to clump. 
   It is opined by Applicants that an increased paddle angle  220  may increase the frictional forces  224  between the metered material  112  and the paddle  164 . That is, centrifugal acceleration acting on the metered material  112  may have a normal component  226 , which in turn increases the frictional forces  224 . This increase in the friction forces  224  may delay the escape of some of the metered material  112  a little longer after release, thus increasing the number of flight paths  198  directed towards the lateral fringes  214  of the distribution curve  200 . 
   The adjustment mechanism may provide the various paddle angles  220  in any suitable manner. In certain embodiments, the adjustment mechanism  218  has a pivot  228  and clamp  230  sliding in a slot  232 . The slot  232  may define the range of the paddle angles  220 . The clamp  230  may secure the paddle at the desired location. In one embodiment, the clamp  230  is a bolt  230  that may be tightened to squeeze the paddle  164  against the disk  160 . In selected embodiments, the bottom plate  170  may be modified or even omitted to provide a user with access to the clamp  230  to easily and quickly change the paddle angle  220 . 
   Referring to  FIG. 21 , after a paddle  164  is emptied, it typically passes again behind the shroud  172 . The location where a paddle  164  passes behind a shroud  172  may result in a dangerous pinch point  234 . That is, a foreign object  236  may inadvertently be introduced between the rotating paddle  164  and the shroud  172 . The speed and inertia of the rotating disk  160  and paddle  164  may damage the foreign object  236 , the spinner  142  itself, the shroud  172 , or any combination thereof. A foreign object  236  such as a finger or toe may even be severed at the pinch point  234 . 
   Referring to  FIGS. 22-23 , in certain embodiments in accordance with the present invention, a guard  238  may be added to the spinner  142  to eliminate or reduce the hazardous potential of the paddle/shroud pinch point  234 . In selected embodiments, a guard  238  may be incorporated as part of the shroud  172 . The guard  238  may be made from a material selected to cushion or ameliorate the pinching effect. 
   For example, a guard  238  may secure to the shroud  172  with fasteners  240  and extend away therefrom in a tangential, neutral position  242 . When in use, the guard  238  may be deflected to an activated position  244  where the guard  238  occupies the pinch point  234 . A guard  238  in accordance with the present invention, may be formed of any suitable material. In certain embodiments, flexible, shock absorbing materials may be used. Elastomeric materials and resilient polymers may function well in this application. 
   In certain embodiments, a detent mechanism  246  may be incorporated to hold the guard  238  in the activated position  244 . In one embodiment, a detent mechanism  246  may include extensions  248  on the guard  238  corresponding to apertures  250  formed in the top and bottom plates  156 ,  170 . Thus, when a foreign object  236  begins to be pinched at the pinch point  234 , the detent mechanism  246  may release, permitting the guard  238  to compress or otherwise deflect and absorb the impact. 
   Referring to  FIG. 24 , in other embodiments, the guard  238  may simply extend from the spinner  142  in the neutral position  242 . In general, the guard  238  may be positioned in any suitable orientation with respect to the spinner  142 . In one embodiment, the neutral position  242  is arranged so that the guard  238  extends substantially straight, tangentially from the spinner  142 . The guard  238  may effectively block entrance to the pinch point  234 . Moreover, if a paddle  164  engages a foreign object  236 , then the guard  238  may deflect to cushion or even eliminate the shearing effect. 
   In certain embodiments in accordance with the present invention, the probability of a pinch point  234  injury or damage may be lowered by making it more difficult for a foreign object  236  to be introduced into the pinch point  234 . For example, a spacing  254  may be introduced between the exterior of the spinner  142  and the pinch point  234 . The spacing  254  may be the result of the particular orientation of the guard  238  with respect to the pinch point  234 . That is, in certain embodiments, the guard  238  may extend tangential from the spinner  142  to create the spacing  254 . 
   In other embodiments, the spacing  254  may be generated by extending the top plate  156 , bottom plate  170 , or both. Various combinations of a guard  238  and extension of the plates  156 ,  170  may be used together to create the spacing  254 . In one embodiment, the top plate  156  may extend to form a projection  255  while a guard  238  may extend along to the projection  255  to generate a selected spacing  254 . If desired, the projection  255  may not be formed on the bottom plate  170  to preclude buildup of the metered material  112  thereon. 
   In selected embodiments, extensions  248  on the guard  238  may be included for purposes other than a detent mechanism  246 . Rather, the extensions  248  may resist introduction of the guard  238  between the top plate  156  and the bottom plate  170 . For example, the extensions  248  have a height greater than the vertical spacing between the top and bottom plates  156 ,  170 . Thus, the extensions  248  may resist introduction of the guard  238  into the interior of the spinner  142  and facilitate removal of a foreign object  236  from the pinch point  234 . 
   Referring to  FIG. 25 , in certain embodiments, once the detent mechanism  246  is released, the guard  238  illustrated has a tendency to return to its neutral position  242 . In other embodiments, the guard  238  begins in the neutral position  242  and deflection therefrom tends to be resisted by the resiliency of the guard  238 . In either case, the resilience urging the guard  238  to return to the neutral position  242  may generate a restoring force  252  positioned to urge the withdrawal of the foreign object  236  from the pinch point  234 . In such an embodiment, the guard  238  may thus simultaneously absorb impact and urge or assist removal of the foreign object  236  from the pinch point  234 . 
   Referring to  FIG. 26 , principles of the present invention may be applied to all kinds of spreaders  10 . While emphasis has been placed on drop spreaders, broadcast spreaders, and combinations thereof, various types of distributors  16  may be incorporated within the scope of the present invention. For example, in certain embodiments, a roller brush  256  may be used. The roller brush  256  may be driven in a rotational direction  258  about an axis  260  extending in the lateral direction  11   b  so as to propel the metered material  112  onto the ground surface  144 . 
   Referring to  FIG. 27 , the various components of the present invention may be urged in any suitable manner. Suitable power systems may be electric, hydraulic, pneumatic, internal combustion, and/or human. Additionally, power may be derived from other sources. For example, rotational motivation may be diverted from a power take off or from the rotation of the wheels of a spreader  10  as it is towed. 
   In certain embodiments, a hydraulic system  261  may be used. Various hydraulic designs may be used and still accomplish the same end result. In one such design, a pump  262  may extract fluid from a reservoir  264  and urge the fluid into hydraulic lines  266 . When a solenoid valve  268  or other type of valve  268  is properly positioned, the pump  262  may push fluid through a flow control valve  270 . The flow control valve  270  may variably control the amount of fluid traveling to, and thus the rotational speed of, various hydraulic motors  150 . The number of motors  150  selected may correspond to the number of spinners  142 , roller brushes  256 , or the like used by the spreader  10 . 
   Once the fluid has passed through the motors  150 , it may be reunited with the excess from the flow control valve  270  and enter a second flow control valve  272 . If a second solenoid valve  274  is properly aligned, the fluid metered from the second flow control valve  272  may variably control the amount of fluid traveling to, and thus the rotational speed of, a second motor  66 . The second motor  66  may provide the necessary motivation for the carrier  34 . Fluid leaving the second motor  66  may then reunite with the excess from the second flow control valve  272  and return to the reservoir  264  by passing through a filter. A pressure relief valve  278  may be added to protect the hydraulic system from over-pressure. 
   Referring to  FIG. 28 , the performance of a spreader  10  in accordance with the present invention may be illustrated in a chart  279  to provide a user with useful information. The application rate for the present invention may be controlled by manipulating two variables, the speed of the carrier  34  and the speed of the spreaders. 
   For example, with a hydraulic power system  261 , when the first control valve is fixed at a particular setting, various settings of the second flow control valve  272  controlling the speed of the carrier  34  may be plotted on the horizontal axis  280 . The vertical axis  282  may be scaled to represent the application rate of the metered material  112 . Data points corresponding to the application rate at various pairings of second flow control valve  272  settings and speed of a spreaders may be plotted. Curves  286  may connect the data points corresponding to a particular speed of a spreader. 
   When a user desires to apply material  112  at an application rate of four cubic feet per 1000 square feet of ground surface  144 , the user may set the second flow control valve  272  at three and a half and drive the spreader  10  at two miles per hour. Alternatively, the user may set the second flow control valve  272  at approximately five and drive the spreader  10  at four miles per hour. Various other combinations may also achieve the same application rate. Thus, the user by simply knowing and controlling two variables, may determine the rate at which the material  112  is being applied. 
   The relatively flat regions  288  on the plotted curves  286  are characteristic of a particular hydraulic power system  261  and may not be present when other power systems  261  are used. That is, a certain amount of fluid flow is required for the carrier  34  to start motion. This threshold in the illustrated example corresponds to a second flow control valve  272  setting valve of two. Similarly, a second flow control valve  272  setting valve of five and above does not significantly change the speed of the carrier  34 . A setting of five must be near the maximum throughput of the second control valve  272 . Thus, it may be useful to plot a chart  279  for each power system  261  having significantly different operating parameters. 
   The present invention may be embodied in other specific forms without departing from its essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes within the meaning and range of equivalency of the claims are to be embraced within their scope.