Abstract:
Disclosed herein is a belt assembly including a flexible belt with an improved belt attachment. The belt attachment includes two crossbars spaced along the length of the belt. The crossbars retain bearings that allow predetermined movement in six degrees of freedom. The crossbars are connected by a rigid body that attaches to the bearings. Implements that are attached to the rigid body are simply supported but restrained in pitching rotation.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with Government support under grant Award Number DE-EE0005412 awarded by the U.S. Department of Energy. The Government has certain rights in the invention. 
    
    
     BACKGROUND 
     This application relates to belt attachments, specifically to an improved system for belt attachments that sustain large loads and very high cycle fatigue. Typical applications include conveyors, bucket excavators, elevators, vertical lifts, and similar machines used to transfer a load from one location to another. Belt attachment systems may also be used in power conversion machines, such as in hydropower or wind power devices, where it is desired that large loads are passed from an attached body to a belt that then drives a generator. However, currently available belt attachment systems lack the ability to withstand large loads and high cycle fatigue. 
     Chains have been used in place of belts for some systems, but chains tend to be heavy, consist of many moving parts, and suffer from high wear rates and high maintenance cost. Due to these issues, chain-based systems often demand frequent maintenance. Chain systems also require complex systems to maintain chain tension as the system wears. 
     Belt systems have advantages over chain systems including relative simplicity, lower maintenance requirements, and reduced noise. Belt attachments can be used on a single belt with attached bodies as is typical of conveyor systems. In this case, loads tend to be light relative to the size and power rating of the belt and loads are typically transferred along the flat portion of the belt. Belt attachments can also be used to support attached bodies between a plurality of belts such as in vertical lifts. In this case and with heavier loads, rigid attachments to the belt can suffer from bending moment induced stresses resulting in relatively low fatigue lifetimes. 
     Current methods used to secure a single attachment to a belt are generally unsatisfactory for the transfer of large loads and high fatigue lifetimes. Some common securing methods include fastening (bolts or rivets), gluing, and vulcanizing. Bolts or rivets that, by themselves, secure attachments suffer from low belt fatigue lifetimes by gradually elongating the through holes in the belt. Gluing is a messy process and does not allow the attachment to be removed from the belt. Furthermore, glue degrades and breaks down relatively quickly in operation due to peeling forces as the bch bends around the sprocket. Vulcanizing elastomeric members to a belt requires special tooling and the resulting attachments do not support large loads. 
     Other methods of belt attachment have been used to address the issue of supporting the attachment as it goes around the sprocket. This is a problem area for many attachment methods because the flat contact area changes to a line contact around the sprocket and is therefore not capable of supporting a pitching moment. Also, the straight-line distance between two adjacent belt teeth changes around the sprocket, which makes multiple attachment points difficult. Existing solutions either support, relatively low loads or suffer from high wear rates. 
     Different belt attachment systems and different applications require different boundary conditions for connecting an implement to the belt attachment(s). A single belt attachment may need to allow, restrain, or fix six degrees of freedom. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a belt attachment in accordance with a first aspect. 
         FIG. 2  is an exploded view of the belt attachment shown in  FIG. 1 . 
         FIG. 3  is a schematic cross sectional view of the belt attachment shown in  FIG. 1 . 
         FIG. 3A  is a detailed cross sectional view from  FIG. 3 . 
         FIG. 4  is a second schematic cross sectional view of the belt attachment shown in  FIG. 1 . 
         FIG. 5  is a schematic orthogonal cross section view of the belt attachment shown in  FIG. 1 . 
         FIG. 5A  is a detailed cross sectional view from  FIG. 5 . 
         FIG. 6  is a view of a crossbar showing the spike (“crampon”) features. 
         FIG. 7  is an isometric view of a belt attachment in accordance with a second aspect. 
         FIG. 8  is an isometric view of a belt attachment in accordance with a third aspect. 
         FIG. 9  is an isometric view of a parallel belt system in accordance with a fourth aspect. 
         FIG. 10  is an isometric view of a single belt conveyance system in accordance with a fifth aspect. 
         FIG. 11  is a detail section view of the aspects shown in  FIGS. 9 and 10 . 
         FIG. 12  is an isometric view of a dual belt conveyance system in accordance with a sixth aspect. 
         FIG. 13  is an isometric view of a belt conveyance system in accordance with a seventh aspect. 
         FIG. 14  is a chart of belt attachment design variables versus crossbar pitch spacing. 
     
    
    
     PARTS LIST 
       100  Belt attachment assembly 
       101  Belt 
       102  Crossbar 
       103  Platform 
       104  Bearing cap 
       105  Spring washer stack 
       106  Fasteners 
       107  Through belt fasteners 
       108  Nuts 
       109  Threaded hole 
       116  Lift direction 
       117  Drag direction 
       118  Side direction 
       119  Pitching rotation 
       120  Cocking rotation 
       121  Rolling rotation 
       122  Belt surface 
       123  Tensile member 
       201  Second spring washer stack 
       202  Pin 
       203  Inner cylinder 
       204  Middle cylinder 
       205  Outer cylinder 
       206  Washers 
       207  Belt pocket 
       208  Hole through belt 
       209  Bearing cavity 
       210  Crossbar holes 
       300  Bearing assembly 
       301  Belt pitchline 
       302  Pin center 
       303  Fin offset 
       304  First gap 
       305  Second gap 
       306  Third gap 
       307  Fourth gap 
       308  Ramps 
       310  Crossbar spacing 
       311  Pin outer surface 
       312  Inner cylinder inner surface 
       313  Inner cylinder outer surface 
       314  Middle cylinder inner surface 
       315  Middle cylinder outer surface 
       316  Outer cylinder inner surface 
       317  Outer cylinder outer surface 
       401  Spikes 
       402  Fastener shank 
       403  Fastener thread 
       404  Crossbar to belt interface 
       501  Rib 
       700  Belt attachment assembly 
       800  Belt attachment assembly 
       801  Elastomeric cylinder 
       802  Elastomeric bearing 
       900  Conveyor system 
       901  Implement 
       902  Parallel belt assemblies, spaced apart 
       903  Points of attachment 
       904  Sprockets or sheaves 
       905  Linear portion 
       906  Curved portion 
       1000  Conveyor system 
       1001  Implement 
       1002  Belt assembly 
       1003  Point of attachment 
       1010  Belt 
       1020  Crossbar 
       1021  Crossbar 
       1030  Platform 
       1031  Platform 
       1040  Bearing cap 
       1041  Bearing cap 
       1101  Belt attachment 
       1103  Implement attachment boils 
       1105  Pay load center of mass 
       1106  Belt pitch line 
       1107  Distance between payload center of mass and belt pitch line 
       1200  Conveyor system 
       1201  Point of attachment 
       1202  Belt assembly 
       1203  Load-bearing implement 
       1204  Sprocket or sheave 
       1205  Lifting module 
       1206  Lifting module 
       1207  Payload (pallet or other load) 
       1220  Belt surface 
       1300  Conveyor system 
       1301  Load-bearing platform 
       1302  Belt assembly 
       1303  Point of attachment 
       1304  Load angle 
       2020  Pin 
       2021  Pin 
       2030  Inner cylinder 
       2050  Outer cylinder 
       2091  Bearing cavity 
       3020  Pin center 
       3030  Pin offset 
       3100  Crossbar spacing 
     DETAILED DESCRIPTION 
     Belt attachments are used to connect various implements such as buckets, blades, or rigid platforms to a belt for either driving the implements or using the implements to drive the belt for the generation of power. Depending on the specific application, a single belt attachment can restrain the implement within predetermined limits, or fix the implement with six degrees of freedom. These six degrees of freedom are defined herein. 
     There are three translational degrees of freedom and three rotational degrees of freedom. As shown in  FIG. 1 , a load orientated in-line with the travel of the belt, parallel to lift direction  116  (Z-axis) is a “lift load” and will nominally result in a “lift translation.” A load orientated perpendicular to the back of the belt, parallel to drag direction  117  (Y-axis) is a “drag load” and will nominally result in a “drag translation.” A load orientated transverse to the direction of travel of the belt, i.e. parallel to side direction  118  (X-axis), is a “side load” and can result in a “side translation.” A moment that occurs about an axis transverse to the direction of travel of the belt, i.e. a moment about side direction  118  (X-axis), will be termed a “pitching moment” and can result in a “pitching rotation”  119 . A moment that occurs about an axis normal to the back of the belt, i.e. a moment about drag direction  117  (Y-axis), will be termed a “cocking moment” and will nominally result in a “cocking rotation”  120 . A moment that occurs about an axis in-line with the direction of travel of the belt, i.e. a moment about lift direction  116  (Z-axis), will be termed a “rolling moment” and will nominally result in a “rolling rotation”  121 . It is further understood that these directions will travel with and remain relative to the belt regardless of the belt being in a straight or curved section. 
     These six degrees of freedom should be considered in the design of a successful belt attachment. For example, a pair of parallel belts with a spanning implement can experience large loads in both the lift and drag directions as well as large pitching moments. In this case, it is desirable to have the implement be simply supported in both primary bending directions by restricting the lift translation and drag translation on each belt attachment while allowing for predetermined cocking rotation, rolling rotation, and side translation. At the same time, it is important to resist pitching moments by constraining pitching rotation. Finally, when transferring high loads, a pair of sprockets connected by a cross-shaft will experience windup, which can result in an angular misalignment between sprockets. This effect, combined with manufacturing tolerances, requires the belt attachments to accommodate a small drag translation. Other applications can impose different constraints on the belt attachment. 
     Belt attachments typically operate in demanding applications that could include high loads and moments, very high cyclic loads over millions of cycles, adverse environments including marine and heavy industry, tight space constraints, or any combinations of the foregoing. In addition, it is desirable that belt attachments operate continuously with little to no maintenance. 
     In one aspect of the invention shown in  FIGS. 1-6 , belt attachment  100  can accommodate multiple degrees of freedom and operate in various demanding applications. Belt attachment  100  is designed for applications where it is desired to resist pitching moments of implements. Pitching moments  113  are resisted in this aspect by two belt attachment points in the lift direction  116 . These two attachment points are accomplished by attaching two crossbars  102  to a belt  101  using pre-drilled belt through-holes  208  and fastening hardware consisting of fasteners  107 , washers  206 , and nuts  108 . A belt cutout  207  can be provided to accept the recessed bearing cavity  209  on the crossbar  102 . The crossbars  102  are preferably positioned at the center of belt teeth so that washers  206  and fastener  107  heads are completely contained within the tooth profile. This allows the belt  101  to travel over a sprocket without modification to the sprocket. In another aspect, crossbars  102  can be positioned at other locations along the lift direction  116  of the belt. In this aspect, sprockets may require grooves to pass the hardware. 
     Fasteners  107  can have a shank portion  402  and a threaded portion  403 . Crossbar holes  210  can preferably be made to have a locational clearance fit with the shank portion  402  of the fasteners  107 . Where high cyclic loads are anticipated, the locational clearance fit significantly reduces the stresses in the threaded portion  403  of the fasteners  107 . Due to the compliant nature of belts, washers  206  can be used to distribute the fastener load over a larger area and prevent fastener pull-through. Many other types and configurations of fasteners are possible for attaching the crossbars  102  to the belt  101 . Examples of different types of fasteners include, but are not limited to, regular bolts and screws with different head shapes, rivets, studs, and shoulder bolls. Examples of different configurations of belt attachment  100  include: using a threaded crossbar  102 ; securing the fasteners with various types of locknuts, jam-nuts or lock-washers; omitting or using various kinds of washers or spring washers, or any combination of the foregoing. 
     The belt to which the attachments are affixed may include “timing” or positive drive belts, flat belts, or “V” belts, with or without reinforcing material. The belt may be manufactured of any common belt material, and can include flexible material such as, but not limited to, polyurethane, rubber, or neoprene. The belt may also be combined with reinforcing material such as, but not limited to, steel or stainless steel wire or cable, or fibers such as, but not limited to, Kevlar, carbon, or fiber glass. 
     Contact between the crossbar  102  and belt  101  can be augmented with substantially pyramidal shaped spikes  401  that can engage belt  101 . For belts that are reinforced with tensile members  123  such as steel, Kevlar, glass fiber or carbon fiber, it is desirable to design the spikes  401  to engage the tensile members  123  without cutting through them. The spikes  401  can be patterned around the belt through-holes  208  to fall within the belt area covered by the washers  206 , so that belt  101  and tensile members  123  are sandwiched between the washers  206  and crossbars  102 , thus ensuring lull engagement of the spikes  401 . 
     In applications with high loads such as those corresponding to the maximum rated belt power for a given belt speed and/or very high cycle fatigue endurance on the order of tens of millions of cycles, the spikes  401  have not been observed to slip or fracture. In one aspect, spikes  401  withstood belt attachment loads of 9000N on a belt rated for 250 kW for 100 million load cycles without failure. Spikes  401  can also be placed in additional locations on the underside of the crossbar  102 . 
     As shown in  FIGS. 2-6 , the bushing roller bearings  300  include a pin  202 , an inner cylinder  203 , a middle cylinder  204 , and an outer cylinder  205 , with cylinders  203 ,  204 ,  205  disposed concentric to and along the mid-span of the pin  202 . For example, pin  202  is contained within an inner area of inner cylinder  203 ; pin  202  and inner cylinder  203  are contained within an inner area of middle cylinder  204 ; and pin  202 , inner cylinder  203 , and middle cylinder  204  are contained within an inner area of outer cylinder  205 . The bearing subassembly is comprised of two sets of bushing roller bearings  300  disposed between two platforms  103 . It is also possible to use just one cylinder, two cylinders, four cylinders, five cylinders, six cylinders, or more than six cylinders in bushing roller bearings  300 . The pins can be press-fit at both ends to the two platforms, or could be connected by brazing, welding, swaging, heading, fasteners, as well as other methods known to those skilled in the art. In one aspect, a sandwiched pair of spring washer stacks  105  and a sandwiched second pair of spring washer stacks  201  can be used. 
     The bearing subassembly spans the two crossbars  102  and is attached to them so that the outer cylinders  205  of the bearings are sandwiched between a bearing cavity  209  in the crossbar  102  and a mating bearing cavity in a bearing cap  104 . The spring washer stacks  105  and  201  can be disposed on the outside of the bearing cavity  209  and adjacent to ribs  501  in the crossbars  102  and matching ribs in the bearing caps  104 . The bearing caps  104  are held in contact to the crossbars  102  with fasteners  106  that engage threaded holes in the crossbars  102 . The bearing caps  104  and crossbars  102  can also have mating ramps  308  that help align the bearing cavities  209 . The ramps  308  can prevent relative movement between the bearing caps  104  and crossbars  102  in the lift direction  116  and can allow the crossbars  102  to sustain higher stresses. Other methods of attaching the bearing caps  104  to the crossbars  102  are acceptable such as rivets, bolts and nuts, brazing, welding, clips, and other methods known to those skilled in the art. 
     Further detail for bushing roller bearings  300  is shown in  FIG. 3A . The three concentric cylinders  203 ,  204 , and  205  are separated from the pin  202  and from one another by three small gaps. Gap  304  is positioned between pin  202  and inner cylinder  203 . Gap  305  is positioned between inner cylinder  203  and middle cylinder  204 . Gap  306  is positioned between middle cylinder  204  and outer cylinder  205 . These gaps ensure slip fits and allow the cylinders  203 ,  204 , and  205  to translate and rotate relative to the pin  202 , bearing cavity  209 , and one another. In one aspect of the invention, the gaps range in size from approximately 0 mm to approximately 0.5 mm. In another aspect, the gaps range in size from approximately 0.02 mm to approximately 0.3 mm. In a further aspect, the gaps range in size from approximately 0.05 mm to approximately 0.2 mm. The gaps  304 ,  305 , and  306  can also be defined to allow predetermined angles of cocking rotation  120  and rolling rotation  121 . For example, if significant cocking rotation  120  or rolling rotation  121  are expected, gaps  304 ,  305 , and  306  could be increased by, for example, increasing the size of the bearing cavity  209  and diameters of cylinders  203 ,  204 , and  205 . Increasing the gaps  304 ,  305 , and  306  allows the belt attachment  100  to absorb rotations without transferring cocking moments  114  or rolling moments  115  to the belt  101 . In this example, gaps  304 ,  305 , and  306  could also be set to allow predetermined angles of rotation and prevent further belt attachment cocking  120  or rolling rotation  121 . Bearing cavity  209  is formed by crossbar  102  and bearing cap  104  and is the area between either crossbar  102  or bearing cap  104  and outer cylinder  205 . Gap  307  can be positioned in bearing cavity  209  between outer cylinder  205  and either crossbar  102  or bearing cap  104 . As shown in  FIG. 3A , in one aspect the bearing cavity  209  formed by crossbar  102  and bearing cap  104  is not perfectly circular, but is defined by two tangent are segments of different radii. This is in contrast to bushing roller bearings that are housed in a circular cavity. In this aspect, gap  307  is therefore not of uniform thickness around the circumference of the bearing  300 . The shape of the bearing cavity  209  can thus be designed to allow for different amounts of pin  202  translation in the lift  116  and drag directions  117 , and/or to limit cocking rotation  120  and rolling rotation  121  independently. In one aspect of the invention, additional gap thickness is needed in the lift direction  116  to accommodate travel around the sprocket where the straight line distance between the two crossbars  102  changes. In this aspect, it is desirable to keep translation in the drag direction  117  to a minimum to minimize pitch rotation  119 . Some translation in the drag direction  117  is required, however, to allow for rolling rotation  121 , free moving cylinders, tolerances, and any sprocket misalignment due to windup or tolerances. In another aspect of the invention, it might be desirable to allow a predetermined amount of pitching rotation  119  by increasing the size of the gaps in the drag direction  117 . 
     The crossbar spacing  310  shown in  FIG. 3  and depends on several factors. In one aspect, crossbar spacing  310  is two belt pitches, with one pitch being defined as the distance between adjacent belt teeth. For a given pitching moment, placing the crossbars  102  closer together increases the drag loads and therefore total radial loads on the bearings and increases the pitching rotation  119  of the attached implement. However, placing the crossbars  102  closer together also reduces the side translation that each bearing must accommodate for every belt revolution. Bearing wear is a function of bearing load and sliding distance and therefore changes with crossbar spacing. Crossbar spacing  310  can be optimized for any of these variables or for any other variable of importance. A chart illustrating how design variables vary with crossbar pitch spacing is shown in  FIG. 14 .  FIG. 14  applies (o one specific aspect of the invention where lift loads, drag loads, pitching moments and corresponding rotations and translations are all present. The variables listed are “pin side trans”, “bearing wear”, “pitch rotation”, and “radial load.” “Pin side trans” refers to pin  202  movement in the side direction  118  as a result of cocking rotation  120  and side translation. “Bearing wear” describes the combined rate of wear of the bearing  300  components (pin  202 , concentric cylinders  203 ,  204 , and  205 , and bearing cavity  209 ) for a bushing roller bearing configuration. “Pitch rotation” refers to pitching rotation  119  of the platforms  103  or attached implement  901 . “Radial load” is the combined bearing radial load due to lift loads, drag loads, and moments. The design variables in the chart are normalized, i.e. each has a maximum value of unity, so that they can easily be compared on a single chart. In this aspect of the invention, the maximum “pin side trans” is 2.5 mm, the maximum “bearing wear” is 0.08 mm^3/hr, the maximum “pitch rotation” is 1.2 degrees, and the maximum “radial load” is 6300 N. 
       FIG. 14  illustrates how crossbar spacing could be selected for a given application. For example, in applications with high pitching moments, the crossbar spacing could be increased to reduce bearing radial loads and pitching angles at the expense of increased bearing wear and pin side translation. In this application, crossbar spacing could conceivably be increased to a value corresponding to the sheave  904  diameter, which in one aspect is twelve belt pitches. If, however, pin side translation is limited by geometrical constraints or deflection of spring washer stacks  105  or  201 , a lower crossbar spacing could be selected. In applications where bearing lifetime is the highest priority, a crossbar spacing could be selected to minimize bearing wear. For the loading scenario shown in  FIG. 14 , the optimal range for minimizing bearing wear is approximately two to approximately three belt pitches. In one aspect of the invention, the belt can have a pitch of 32 mm and a crossbar spacing  310  of 64 mm (2 pitches). In another aspect of the invention, a smaller belt can have a pitch of 14 mm and crossbar spacing of 42 mm (3 pitches.) For belts without teeth, the crossbar spacing  310  can be similarly optimized for any variable of importance. 
     Operation 
     The belt attachment  100  shown in  FIGS. 1-6  can be used with a set of parallel belts  902  with an implement  901  supported between two belt attachments  100  at attachment points  903 , as shown in  FIG. 9 . Various implements such as buckets or blades can be attached to the belt attachments using the threaded holes  109  in the platforms  103 . Other methods of attaching implements  901  to the platforms  103  are possible such as through-bolts with nuts, brazing, welding, making the platforms and implement an integral single part, or other methods known to those skilled in the art. Depending on the application, the implement  901  can be driven by the belts  902 , or the implement  901  can drive the belts  902  to produce power. In either case, loads and moments are imposed on the implements  901  that transfer to the belt  902  through the belt attachments  100 . 
     During a typical cycle, belt attachments  100  travel over a linear portion  905  and then over a curved portion  906  as they travel over the sprockets  904 . Rotational movement around sprocket  904  requires each bearing  300  to allow for a predetermined pitching rotation as well as a lift translation due to the change in straight line distance between crossbars  102  over the sprocket  904 . This combined movement of bearing surfaces results in sliding contact between bearing elements, which include the pin  202 , inner cylinder  203 , middle cylinder  204 , outer cylinder  205 , and bearing cavity  209 . This sliding contact results in wear. In the case of a normal bearing that is fixed to its housing, wear would occur at the same location with each cycle, resulting in rapid localized wear. However, for bearings  300 , the bearing cylinders  203 ,  204 , and  205  experience a net rotation with every cycle and thereby distribute wear evenly over all cylinder bearing surfaces: pin outer surface  311 , inner cylinder inner surface  312 , inner cylinder outer surface  313 , middle cylinder inner surface  314 , middle cylinder outer surface  315 , outer cylinder inner surface  316 , outer cylinder outer surface  317 , and bearing cavity  209 . In other words, the cylinders distribute the wear over a larger contact area leading to longer maintenance intervals. While wear is a function of force and sliding distance, it is also a function of adhesion between mating materials. Adhesive wear is caused by micro-welding and sliding induced rupture between opposing asperities on the rubbing surfaces of mating bodies. Similar materials tend to experience a greater degree of attraction and adhesion than dissimilar materials. Therefore, in one aspect of the invention, dissimilar materials can be used for adjacent parts and cylinders to reduce adhesive wear. In one aspect of the invention, adjacent parts can be formed of steel and bronze. For example, the pin  202  can be steel, the inner cylinder  203  can be bronze, the middle cylinder  204  can be steel, the outer cylinder can be bronze, and the bearing cavity  209  can be steel. In another aspect, if the pin  202 , inner cylinder  203 , middle cylinder  204 , outer cylinder, and bearing cavity  209  are all made of steel, adhesive wear would be approximately two orders of magnitude greater than when dissimilar materials are used for adjacent parts, depending on the specific materials and whether lubricant is used between adjacent surfaces. Any bearing materials known to those skilled in the art could be used for any of the cylinders, including: steel; stainless steel; copper alloys, polymers; composites, including impregnated metals, reinforced plastics, tri-metals, and coated materials. Lubricants such as grease, oil, water, or graphite, or others could also be packed between bearings to reduce adhesive wear. 
     As shown in  FIG. 9 , it is typical during operation for lift, drag, and moment loads to be placed on implements  901  during linear travel and then for these loads to change over the sprockets  904 . Lift loads result in a lift translation of the pins  202  relative to the bearing cavities  209 . This causes the bearing cylinders  203 ,  204 , and  205  to be forced against the smaller diameter portion of the bearing cavity  209  causing the cylinders  203 ,  204 , and  205  to bend like a set of leaf springs. Because the bearing cylinders  203 ,  204 , and  205  act like springs during lift, loads, resultant impact forces are reduced. In one aspect of the belt attachment pins  202  can be nominally situated at the center of the bearing cavity  209  with the belt  101  in a linear position, as shown in  FIG. 3 . This allows lift loads to be taken evenly by each of the bearings  300  during the linear portion  905 . For lower lift loads, the pins  202  could be offset in opposing lift directions relative to the bearing cavities  209  to reduce lift translation during the linear travel sections. In  FIG. 3 , this offset configuration would have the right pin  202  offset to the right side in its bearing cavity  209  and the left pin  202  offset to the left side in its bearing cavity  209 . 
     Lift loads on implements  901  can also result in the implement  901  bending unless it is perfectly rigid. Bending of the implement  901  manifests itself as a cocking rotation  120  of the belt attachment  100 . At the bearings  300 , this is seen as a side translation and cocking rotation  120 . The amount of side translation is different from one pin  202  to the other pin  202  depending on where the centroid of the implement  901  is located relative to the platform  103  in the lift direction  116 . Spring washer stacks  105  and  201  can be used to absorb the side translation and at the same time provide a restoring centering force. Depending on the amount of side translation expected per pin, the spring washer stacks  105  or  201  can be configured to provide a high centering force and low displacement or low centering force and high displacement. For example, spring washer stacks  105  could be made from steel and spring washer stacks  201  could be made from plastic if the pin  202  corresponding to the plastic washers  201  experiences much greater side translation than the pin  202  corresponding to the steel washers  105 . The spring washer stacks  105  and  201  can also act to seal and isolate the bearings  300  from the surrounding environment. In another aspect of the invention, when the spring washer stacks  105  and  201  are not needed for their sealing or centering functions, they can be omitted. Many other types of springs could be used to provide the centering force such as other types of spring washers, regular compression springs, various types of cantilever springs, elastomeric elements or other methods known to those skilled in the art. In addition, a bonded elastomer, bellows, boot, or other method could be used to seal and isolate bearings  300  from the surrounding environment. 
     Lift loads can also result in a pitching moment  113  of the crossbar  102  relative to the belt  101 . The lift load  110  will be reacted at the pin center  302  where it contacts the bearing cavity  209 . In  FIG. 3 , the offset  303  of the pin center  302  is shown relative to the pitch line of the belt  301 . As shown, the pin center  302  is coincident with the belt surface  122 . Therefore, lift loads will nominally not result, in a pitching moment of the crossbar  102  relative to the belt  101 . This results in negligible pitching rotation of the crossbar  102  relative to the belt  101 , which can lead to lower loads at this crossbar to belt interface  404  and less wear on the belt surface  122 . Having the pins  202  and bearings  300  coincident with the belt surface  122  also requires a belt cutout  207 . In another aspect of the invention for applications where the lift loads are lighter, the pin offset  303  can be increased so that, a belt, cutout  207  is no longer required. An example of this configuration is shown in  FIG. 7 . 
     A lift load on an implement  901  that is not aligned with the pin centers  302 , can manifest itself as a pitching moment on the belt attachment  100  and be taken by the hearings  300  as opposing drag loads. A pitching moment on an implement  901  can also have the same result. Both of these loads will result in a pitching rotation  119  of the belt attachment  100 . The amount of pitching rotation  119  can be limited by reducing the size of the bearing cavity  209  in the drag direction  117  or by increasing the spacing  310  between crossbars  102 . 
     Drag loads on implements can result in rolling rotation  121  and side translation of the belt attachments  100 . Side translation will result in a side translation of the pins  202  relative to the bearing cavities  209 . This translation can be unconstrained or can be absorbed by spring washer stacks  105  and  201 . Rolling rotation of the pins  202  relative to the bearing cavities  209  can be unconstrained until gaps  304 ,  305 ,  306 , and  307  are reduced to zero on either side of the cylinders  203 ,  204 , and  205 . 
     In the conveyor system shown in  FIG. 9 , implements  901  are perpendicular to parallel belts  902 . If implements  901  are not perfectly perpendicular to the parallel belts  902 , during operation, one belt attachment  100  will enter the curved section  906  slightly ahead of the parallel belt attachment  100  as a result of windup between parallel sprockets  904  or assembly tolerances. For the bearings  300 , this can result in a drag translation of pins  202  relative to bearing cavities  209 . Unless the implement  901  is compliant in the twist direction, large bearing forces could result, causing increased wear and eventual failure. Additionally, gaps  304 ,  305 ,  306 , and  307  can be made large enough to accommodate any anticipated twist due to windup or tolerances. In one example, a windup of 1.6 degrees causes a drag translation of 0.45 mm. If the total gap distance resulting from the addition of gaps  304 ,  305 ,  306 , and  307  is equal to or greater than 0.45 mm, bearing forces due to windup are eliminated. In the aspect shown in  FIG. 3 , each of the three gaps  304 ,  305 , and  306  are nominally 0.1 mm with gap  307  being absent in the drag direction. If in this aspect the drag translation caused by windup is 0.45 mm, the additional 0.15 mm is taken up by compliance of implement  901  in twist. 
     The aspect of the belt attachment as described and shown in  FIGS. 1-6  does not substantially constrain cocking rotations, rolling rotations, or side translations. This results in simple support constraints of the attached implement  901  at the two belt attachments points  903 . Simple supports are well known beam constraints that allow rotations and therefore do not transfer moments. These simple constraints are coincident with the mid-span of the belt  902  in the side direction  118  and the belt surface  122  in the drag direction  117 . The constraints therefore provide for an evenly distributed force along the width of the belt  902  and minimal transfer of moments to the belt  902 . Belt  902  and belt attachment  100  fatigue lifetimes can therefore be substantially increased over prior art designs. At loads corresponding to the maximum rated belt power for a given belt speed, fatigue lifetimes of the belt and entire belt attachment have been observed to reach several tens of millions of cycles without failure. 
     In another aspect of the invention, belt attachment  700 , shown in  FIG. 7 , is designed to resist cocking  114  and rolling moments  115  in addition to pitching moments  113 . Belt attachment  700  accomplishes these additional restraints through placement of the bearing inner and outer cylinders  2030  and  2050  at the ends of the pins  2020 . The bearing caps  1040  are split and put at the ends of the pins  2020 . The platform  1030  is a single part and is placed at the center of the attachment  700 . In certain applications, belt attachment  700  can support loads in certain orientations, such as cantilevered loads, for example as shown in  FIG. 13 . Belt attachment  700  can also provide additional cocking stability for a centrally-supported configuration, for example, as shown in  FIGS. 10 and 12 . 
       FIG. 7  also includes several other aspects of the invention. For example, belt  1010  in  FIG. 7  does not include cutouts, as all of the attachment system  700  is located above the back of belt  1010 . This design preserves the tensile reinforcements in belt  1010 , and reduces manufacturing steps. However, belt attachment  700  is preferable for lower load cases where the resulting moment between crossbar  1020  and belt surface  1220  is acceptable. This moment is caused by pin offset  3030  in  FIG. 7  being greater than pin offset  303  shown in  FIG. 3 . The pin offset  303  results in zero moment because pin center  302  is coincident with belt surface  122 . Any pin offset  3030  that is greater than this, i.e. pin center  3020  is offset from belt surface  1220 , will result in a non-zero moment and relative pitching rotation between crossbar  1020  and belt surface  1220 . The architecture shown in  FIG. 7  is possible if the lift loads  110  are low enough or the fatigue cycles are low enough to prevent unwanted belt wear caused by the relative pitching rotation described above. Additionally the attachment  700  illustrated in  FIG. 7  utilizes a smaller spacing  3100  between crossbars  1020 . In this aspect, the crossbar spacing is one belt pitch or 32 mm. This compact spacing reduces the motions undertaken by the bearing components as the system articulates over a sprocket or sheave, but allows for greater implement pitching rotation. 
       FIG. 8  illustrates another belt attachment  800  in accordance with the present invention. This aspect is very similar to belt attachment  100  in  FIGS. 1-6 , with the main difference being the use of a different type of bearing. Rather than utilizing bushing roller bearings  300 , the bearing  802  illustrated in  FIG. 8  is an elastomeric bearing  802 . Bearing  802  has a rigid interior  2021  and exterior cavity  2091  joined together by a bonded elastomer  801 . Exterior cavity  2091  is comprised of matching substantially cylindrical cavities in crossbar  1021  and bearing cap  1041 . In one aspect, bonded elastomer  801  includes concentric laminae comprising alternating strata of elastomeric materials and rigid materials. In another aspect, the number of laminae, materials of composition of each laminae, and relative proportions of the laminae can be altered. Additionally, the laminae can be composed of continuous, or interrupted, segments, as may best fit the intended use, without deviating from the intent of this belt attachment. The elastomeric bearing may be designed in a number of ways, with the elastomeric members performing a combination of functions including sealing of the rigid concentric members, provision of stability, and/or load carrying capabilities. The elastomeric bearing design can be further optimized to allow for different spring rates in the lift, drag, and translation directions. Rigid concentric members consisting of fully cylindrical or partial arc sections can be added or subtracted to increase or decrease stiffness, respectively, in various directions. 
     Description of Conveyor Systems 
     An aspect of a conveyor system  900  is shown in  FIG. 9 . In this aspect, a plurality of implements  901  are attached at attachment points  903  to a pair of belt assemblies  902  arranged in a parallel manner. The belts, and the attachment points  903 , are spaced apart from each other. The belts operate over sprockets  904 . The implements  901  spanning the two belts  902  can take any of a wide variety of forms depending upon the anticipated use of the resulting system. For example, the implement  901  could instead be a rake, for use in a trash rack cleaning device; a platform or a specialized component for use in a conveyance device; a bar for use in a bulk-materials moving machine; and an aero- or hydro-dynamic profile for use in a kinetic energy conversion device, such as a turbine or a fan. In all of these aspects, and others which will be clear to those practiced in the art, the loads on the implement (lift loads, drag loads, and moments) are passed into the belts  902  through the belt attachments (e.g. belt attachment  100 ) of the subject invention, and the resulting strains due to mechanical deformation under stress are borne by the belt attachments (e.g. belt attachment  100 ). The machine described in this aspect may not require both sets of sprockets  904  illustrated. For example, it may be desirable to build a similar machine using one upper axle with two sprockets. This type of arrangement could find use as a trash rack for water intakes, for example, where it is desirable to reduce the number of submerged components in the machine. 
     An additional aspect of a conveyor system  1000  is shown in the machine illustrated in  FIG. 10 . In this aspect, a plurality of implements  1001  are attached at attachment points  1003  to a single belt assembly  1002 . The implement  1001  can take a wide variety of forms in the same manner as described in  FIG. 9 . In this aspect, it may be desirable for the implement or alternate implement to remain at a specific angle relative to the vector of belt travel as shown in  FIG. 10  as a rotation  120  about the Y axis. The implements  1001  illustrated in  FIG. 10  are orientated perpendicular to the vector of belt travel. In other applications, this angle may be any arbitrary value, as dictated by the intended use. For example, in a bulk transport device designed to move materials or fluids from one side of the machine to the other along the X axis, the implements could be attached at an acute angle, such as 45 degrees, relative to the vector of belt travel, by rotation about the attachment Y-axis. To help restrain cocking rotations, belt attachment system  700  can be used, as shown in  FIG. 7 . A benefit of belt attachment system  700  is the simplification of the system by reducing quantity of components required to accomplish the stabilization of the implement  1001  while undergoing motion. For example, typical conveying machines require many additional components such as complex systems of rollers, bearings, guide rails, and supporting framing, to stabilize the load in a recirculating conveyor platform. Many of these complex systems could be eliminated by the incorporation of the belt attachment system (e.g. belt attachment  700 ), since it can inherently provide stability in multiple axes, while also withstanding large loads and high fatigue cycles. 
       FIG. 11  is a detailed cross-sectional view of the implement  1001  and conveyor system  1000  illustrated in  FIG. 10 . An implement  1001  is attached with bolts  1103  to the belt attachment  1101 , which communicates loads to the belt assembly  1002 . The shape of the implement  1001  is largely irrelevant; as mentioned previously this component can be any load-bearing implement as dictated by the intended application. The pay load will, have a center of mass  1105  positioned at a distance  1107  from the belt pitchline  1106 , causing a pitching moment about the belt  1002 . The distance  1107  may be in the direction illustrated, but it may also be zero (coincident), or it may lie on the opposite side of the belt  1002 . Any of these examples will result in some value (including zero) of pitching moment which the belt attachment  1101  must resist. Additionally, dynamic operation may cause moments and loads different from static operation. High pitching moments or pitching rotations could be further accommodated by moving the crossbars  102  of the belt attachment  1101  farther apart on the belt in the lift direction (refer to spacing  310 ). 
     Another aspect of a conveyor system  1200  is shown in  FIG. 12 . A plurality of load-bearing implements  1203  are attached to the belt assembly  1202  by a plurality of attachment points  1201 . The belt assembly  1202  operates around a plurality of sprockets  1204 . These components, combined with structural support components such as bearings and frame components not shown, comprise a module  1205 . Pairs of these modules, such as  1205  and  1206 , operate in an opposed manner to move a plurality of payloads  1207  from one elevation to another. Motions of the system are indicated by the arrows. More than one pair of modules may be configured. In another aspect of the invention, instead of one pair of modules, there could be two or more pairs. These alternate configurations may be desirable to provide for larger load capacity or greater stability, for example. The means of conveyance of the payload  1207  into and out of communication with the lift modules  1205  and  1206  may be accomplished with a large number of possible options, such as conveyor belts or other systems familiar to one skilled in the art of materials conveyance. 
     Another aspect of a conveyor system  1300  is illustrated in  FIG. 13 . In this aspect, a load-bearing platform  1301  is cantilevered off of a belt, system  1302 . The connection between the platform and the belt is provided at the attachment point  1303 . This aspect utilizes the ability of conveyor system  1300  to react to the resulting cantilever moment while providing a load bearing surface  1301  orientated at a stable angle  1304  relative to the belt. To help restrain cocking rotations, belt attachment system  700  can be used, as shown in  FIG. 7 . The platform illustrated is perpendicular to the belt, but the angle  1304  may be fixed at any arbitrary angle that may be desirable fox the intended use. Similar to the discussion for  FIG. 10 , a different angle  1304  may be desirable to transferring materials or fluids in a certain direction. The platform illustrated may also fake the form of any load-bearing component, or system, such as an aero- or hydro-dynamic foil for use in an energy-conversion system such as a fan or turbine; any desired shape for use in a material mixing or stirring application; a platform to convey loads from one elevation to another; or any other such aspect as may be apparent to one skilled in the art.