Patent Publication Number: US-2010126831-A1

Title: Self cleaning belt conveyor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 61/118,225, filed Nov. 26, 2008, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to belt conveyors and, more particularly, to self cleaning belt conveyors. 
     2. Description of the Related Art 
     Typically, during the transporting of glass substrates through vacuum processing chambers, excess deposition material which is sputtered or sprayed onto the substrates tends to deposit on the floor of the sputter area, which usually has spaced apart conveyor wheels protruding through it. This deposited excess material may build up to the point that it clogs up the conveyor wheels, necessitating stopping the processing chamber, venting it, tearing it apart, cleaning it out, replacing parts, and restarting the process. This cleaning interruption leads to much down-time. 
     Currently used chamber configurations for catching the excess material that accumulates during the deposition process include a static lower floor, such as in a conductance limiting tunnel, or a static deposition shield. However, these configurations all require frequent cleaning of the chamber every time an excess amount of material clogs up the chamber operating space. 
     In a fixed-floor chamber arrangement or configuration, it is desirable to have the lower floor as close as possible to the glass substrate so as to avoid backside sputtering caused by deposited material wrapping around the conveyor wheels. However, when the floor is very close to the glass substrate, there is less room for depositing excess material before running out of space, so that the chamber must be cleaned out more frequently. Oftentimes, operators will assume the risk of backside sputtering in order to be able to run the system for longer periods of time without having to interrupt the process to clean up accumulated deposits, thereby compromising process control. 
     Therefore, there is a need for an apparatus and method of transporting substrates through processing chambers that minimizes cleaning of excess deposited material in order to reduce process down-time and enhance process control. 
     SUMMARY OF THE INVENTION 
     Embodiments described herein generally relate to belt conveyors and, more particularly, to self cleaning belt conveyors. In one embodiment, a belt conveyor apparatus for transporting a substrate through a chamber is provided. The belt conveyor comprises at least one endless belt having a conveying surface, wherein the conveying surface comprises one or more raised components for supporting the substrate and maintaining a gap between the conveying surface and the substrate. The belt conveyor further comprises two or more cylindrical shafts coupled with the at least one endless belt wherein the at least one endless belt is tensioned around the two or more cylindrical shafts and wherein the two or more cylindrical shafts are rotatable to move the conveying surface. 
     In another embodiment, a belt conveyor apparatus for transporting a substrate through a chamber is provided. The belt conveyor comprises a frame, at least two drive shafts supported by the frame and connectable to a motor, and at least two parallel chains, wherein each chain is actively engaged with at least two sprockets operatively coupled with the at least two drive shafts. The belt conveyor further comprises a caterpillar track having a conveying surface, wherein the caterpillar track is mounted on the at least two parallel chains such that the caterpillar track is rotatable around the at least two drive shafts during rotation of the at least two drive shafts, and wherein the caterpillar track comprises at least one raised component on the conveying surface to form a gap between the conveying surface and the substrate. 
     In yet another embodiment, an apparatus for transporting a substrate through a chamber is provided, the apparatus comprising a chain driven assembly for rotating a caterpillar track around at least two drive shafts, wherein the assembly is driven by the at least two drive shafts using at least two parallel chains, wherein each chain is mechanically engaged to at least two sprockets coupled with each drive shaft, and wherein the caterpillar track has a conveying surface comprising one or more raised components for supporting the substrate. 
     In another embodiment, a method of conveying a substrate from a starting point to a destination point along a path is also provided, comprising placing a substrate on a belt conveyor. The belt conveyor may comprise a frame, at least two motorized drive shafts supported by the frame and connectable to a motor, and at least two parallel chains, wherein each chain is actively engaged with at least two sprockets coupled with the at least two drive shafts. The belt conveyor may also comprise a caterpillar track, wherein the caterpillar track is coupled with the at least two parallel chains and has a conveying surface comprising at least one raised component for supporting the substrate and wherein the caterpillar track provides a substrate-conveying stretch and a return stretch. The method further comprises rotating the at least two drive shafts to move the sprockets and the at least two parallel chains such that the caterpillar track is driven around the at least two drive shafts, wherein the conveying surface moves along the path and material deposited on the conveying surface peels off of the conveying surface. The substrate moves on the conveying surface along the belt conveyor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
         FIG. 1  is an elevated side view of one embodiment of a self cleaning belt conveyor; 
         FIG. 2  is a cross-sectional view of an embodiment of a self cleaning belt conveyor, as positioned under a chamber sputtering device; 
         FIG. 3  is an enlarged partial side cross-sectional view of a section of one embodiment of a self cleaning belt conveyor; 
         FIG. 4  is an elevated side view of one embodiment of a self cleaning belt conveyor; 
         FIG. 5  is an elevated side view of a slat of a caterpillar track of one embodiment of a self cleaning belt conveyor; 
         FIG. 6  is an elevated side view of a slat of a caterpillar track of one embodiment of a self cleaning belt conveyor; 
         FIG. 7A  is an elevated side view showing detail of one embodiment of a self cleaning belt conveyor; 
         FIG. 7B  is a magnified elevated side view showing detail of one embodiment of a self cleaning belt conveyor; and 
         FIG. 8  is an elevated side view of one embodiment of a self cleaning belt conveyor. 
     
    
    
     It is contemplated that elements disclosed in one embodiment may be beneficially utilized in other embodiments without specific recitation. 
     DETAILED DESCRIPTION 
     Embodiments described herein provide apparatus and methods relating to belt conveyors and, more particularly, to self cleaning belt conveyors. 
     One embodiment of a belt conveyor apparatus described herein provides a conveying surface on a conveying belt comprising one or more raised elastomeric areas thereon for releasably supporting a substrate and facilitating peeling of excess deposited material from the conveying belt. The substrate may be, for example, a glass substrate. The raised elastomeric areas on the conveying surface may support the glass substrate as it is conveyed through a chamber, such as a deposition chamber, and allow for easy removal of the glass substrate from the conveying surface at the point of destination. As the conveying belt bends around the rollers on the return stretch, accumulated excess material, such as a metal, deposited on the conveying surface tends to peel or flake away from the conveying surface and falls to the floor of a deposition zone. The raised elastomeric areas may enhance the peeling of the deposited material from the conveying surface as the conveying belt bends around the rollers. 
       FIG. 1  is an elevated side view of one embodiment of a self cleaning belt conveyor. The belt conveyor  100  comprises at least three rollers  101 ,  102  and  103  positioned in space parallel to each other but not aligned with one another, so as to form a triangular cross section (see  FIG. 2 ). In other embodiments, belt conveyor  100  may comprise four rollers, or five rollers, or more. Rollers  101 ,  102  and  103  may be made of metal such as stainless steel or aluminum. Rollers  101 ,  102  and  103  may be cylindrical in shape and able to be rotated. In one embodiment, rollers  101 ,  102  and  103  may be solid tubes or cylinders. In another embodiment, rollers  101 ,  102  and  103  may be hollow tubes or cylinders. Rollers  101 ,  102  and  103  may be made of a conductive material. In another embodiment, rollers  101 ,  102  and  103  may have an insulating material, such as rubber or an elastomer, surrounding the outer surface of each roller so as to make each roller nonconductive. Alternatively, rollers  101 ,  102  and  103  may be made of a nonconductive material. One of rollers  101 ,  102  and  103  may be driven by, for example, a motor (not shown), while the remaining rollers may be idle. Rollers  101 ,  102  and  103  may be supported by a conveyor frame (not shown). In one embodiment, one or more of the rollers  101 ,  102 , or  103  may have one or more crowns or bumps  325  protruding from their exterior surface to assist in tracking the conveying belt (see  FIG. 3 ). 
     At least one endless conveying belt  104  may be extended and tensioned around rollers  101 ,  102  and  103 . In one embodiment, roller  102  is positioned below and between rollers  101  and  103  so that roller  102  may function as a tensioning mechanism for conveying belt  104 . Conveying belt  104  may be made of metal, which may be thin and solid. In one embodiment, conveying belt  104  may be made of a woven material, such as a fabric or woven metal, and may be reinforced. In yet another embodiment, conveying belt  104  may be made of a material of sufficient roughness so as to cause the material deposited on the conveying belt  104  to grow thicker prior to it peeling or flaking away from the conveying belt  104 . In another embodiment, conveying belt  104  may have a surface treatment applied to it so as to make it less sticky to minimize adhesion of the deposited material. 
     In yet another embodiment, conveying belt  104  may have one or more areas of elastomeric material, such as rubber or silicon, which are raised from the conveying surface  106  so as to releasably support a substrate being conveyed on the conveying belt  104  and to enhance the ability of the conveying surface  106  to shed deposited material. These one or more areas of raised elastomeric material may span the length and width of conveying belt  104 . As shown in  FIG. 1 , conveying belt  104  may have buttons or studs  105  (one exemplary stud is labeled  105  in  FIG. 1 ) made of an elastomeric material, such as rubber or silicon. It should be noted that the raised areas of elastomeric material are not limited to a specific shape, such as buttons or studs. In one embodiment, the raised areas of elastomeric material may be shaped as squares, or stripes, or triangles, or ellipses, or a grid, or any other shape or combination thereof. It should also be noted that the raised areas of elastomeric material are not limited to a specific size. It is desirable that the raised areas of elastomeric material be sufficiently concentrated or close together and span enough of the width and length of the conveying surface  106  of conveying belt  104  so as to releasably support a substrate being conveyed on the conveying belt  104  and to enhance the ability of the conveying surface  106  to shed deposited material. 
     In one embodiment, multiple endless conveying belts may be positioned adjacent to one another and extended under tension around the motorized roller and the at least two other rollers. It is desirable that for embodiments of the belt conveyor having multiple belts around the rollers, there is little to no space between each adjacent belt, so as to not expose the areas under the belt and within the belt conveyor to deposited material in situations where, for example, the conveying belt passes through a deposition chamber. In one example, four endless conveying belts may be placed side-by-side and extended under tension around the rollers. In another example, a dozen endless conveying belts may be placed side-by-side and extended under tension around the rollers. In another embodiment, multiple belts may be positioned longitudinally end to end so as to form one endless conveying belt which can be extended under tension around the rollers. In one embodiment, each of the multiple belts may have one row of raised areas of elastomeric material, such as elastomeric studs or buttons, as described above. 
     In one embodiment, conveying belt  104  may be grounded. In another embodiment, conveying belt  104  may be floating. In one embodiment, conveying belt  104  may be magnetic. In another embodiment, conveying belt  104  may be nonmagnetic. 
     Rollers  101 ,  102  and  103  may have a diameter sufficiently small to encourage peeling of excess deposited material from the conveying belt  104 , yet sufficiently large to support conveying belt  104  without compromising its structure, depending on the fatigue life and mechanical strength of conveying belt  104 . It is desirable that the diameter of rollers  101 ,  102  and  103  be large enough so that conveying belt  104  has an appreciably long life. 
       FIG. 2  is a cross-sectional view of an embodiment of a self cleaning belt conveyor  200 , as positioned under a chamber sputtering device  220 . Conveying belt  204  extends around rollers  201 ,  202  and  203 . In one embodiment, roller  203  may be driven by a motor (not shown). In another embodiment, roller  201  or roller  202  may be driven by a motor. Although only three rollers are shown in  FIG. 2 , it should be appreciated that more than three rollers may be used in the belt conveyor, as explained above. Conveying belt  204  may be tensioned around rollers  201 ,  202  and  203  in any customary manner. In one embodiment, bottom roller  202  may have adjustable mounting or be adjustable in some other manner so as to serve as a tension mechanism for the conveying belt  204 . Upper conveying stretch  204   a  of the conveying belt  204  between rollers  201  and  203  may carry a glass substrate to the right (as indicated by the arrow) along a predetermined path from a starting point to a destination point. Return stretch  204   b  may be the path formed by conveying belt  204  when looped around roller  202  and tensioned between rollers  201  and  203 . 
     A substrate, such as glass, may be placed on conveying belt  204  such that it is releasably supported by raised areas of elastomeric material, such as elastomeric studs or buttons  205  (only one exemplary stud  205  is labeled in  FIG. 2 ). As shown in  FIG. 2 , it is desirable to have the raised areas of elastomeric material, such as multiple elastomeric studs or buttons, spanning the overall width and length of the conveying surface. It should also be noted, as explained above, that the raised areas of elastomeric material are not limited to a specific shape, such as buttons or studs, or size. In one embodiment, conveying belt  204  conveys a substrate to the right (as indicated by the arrow) along conveying stretch  204   a  while a sputtering device  220  may deposit a material, such as a metal, onto the substrate. Some of the material may also be deposited on the conveying belt  204 . As conveying belt  204  reaches roller  203 , conveying belt  204  will bend around roller  203 , the glass substrate will be released and unloaded from conveying belt  204 , and material of sufficient thickness deposited on conveying belt  204  will peel or flake off of conveying belt  204 , falling to the bottom or floor of the chamber (not shown). In one embodiment, elastomeric buttons  205  will facilitate the peeling of material deposits from conveying belt  204 . In one embodiment, the conveying surface further comprises a surface treatment of a nonstick material to further facilitate the peeling of material deposits from conveying belt  204 . 
     In one embodiment, at least one heat exchanging device, such as a cooling plate, may be located between two or more rollers under a portion or segment of the conveying stretch of the conveying belt opposite the conveying surface. As shown in  FIG. 2 , in one embodiment, at least one primary cooling platen  208  may be located under a portion of conveying stretch  204   a  such that a substrate being conveyed may be cooled to prevent overheating due to chamber conditions. For example, the sputtering device  220  may generate a substantial amount of heat within the chamber. In another embodiment, as shown in  FIG. 2 , secondary cooling platens  209  and  210  may also be placed under portions of the return stretch  204   b  of conveying belt  204 , opposite the conveying surface and within belt conveyor  200 , in order to further cool conveying belt  204 . Any number of secondary cooling platens may be placed under the return stretch  204   b  of conveyor belt  204 , depending on the application. Cooling platens  208 ,  209  and  210  may be cooled using cooling water or other means for cooling. 
     In one embodiment, as shown in  FIG. 2 , the belt conveyor  200  may further comprise a cleaning brush adjacent to a conveying surface of conveying belt  204  at a location on return stretch  204   b  that sweeps the conveying surface to further remove material deposited on the conveying surface. In one embodiment, the cleaning brush may rotate on a roller portion, such as cleaning brush roller  206 , so as to rotate alongside conveying belt  204 . For example, the cleaning brush roller  206  may be located at a spot on the return stretch  204   b  after the conveying belt  204  bends around roller  202 . In one embodiment, the cleaning brush roller  206  may be coupled to some form of driver, such as a motor and an interposed gear box (not shown). In one embodiment, the cleaning brush roller  206  may be independently driven and only activated occasionally. In another embodiment, the cleaning brush roller  206  may be independently driven and activated continuously as the conveying belt  204  rotates around the rollers  201 ,  202  and  203 . In yet another embodiment, the cleaning brush roller  206  may be coupled to the roller  202  by means of a belt  207  so that rotation of roller  202  drives the rotation of cleaning brush roller  206 . In one embodiment, the cleaning brush roller  206  may be overdriven such that it rotates at a faster speed than conveying belt  204 . The cleaning brush roller  206  may rotate in either direction in relation to the travel direction of conveying belt  204  at the location where cleaning brush roller  206  and conveying belt  204  meet. 
     In yet another embodiment, as shown in  FIG. 2 , a shield  211  may be removably attached to the belt conveyor  200  to deflect debris or sputter and prevent the debris from flying onto the trailing edge of a substrate being conveyed as the debris peels from the surface of the conveyor belt  204  or is brushed off from the surface of conveying belt  204 . The shield  211  may be removably secured to the belt conveyor  200  by one or more screws, rivets, or other fasteners. The shield  211  can be made from metal. The shield  211  can be sufficiently long to block any debris from flying onto the trailing edge of a substrate being conveyed, depending on the overall size of the belt conveyor. 
     In one embodiment, a method of conveying substrates from a starting point to a destination point along a predetermined path is provided. Referring to the embodiment of the belt conveyor illustrated in  FIG. 2 , this method comprises placing one or more substrates on a belt conveyor  200 , the belt conveyor having a motorized roller  202  and at least two other rollers  201  and  203 , wherein the motorized roller and the two other rollers are positioned at a distance from one another and in a nonaligned arrangement. In this embodiment, at least one endless conveying belt  204  is tensioned around the motorized roller  202  and the two other rollers  201  and  203 , wherein the conveying belt defines a conveying surface having one or more raised elastomeric areas (see  205 ) thereon for releasably supporting the substrates and provides a substrate-conveying stretch and a return stretch. The motorized roller  202  is operable to drive the conveying belt  204  to move the substrates on the conveying belt along the belt conveyor  200 . This method further comprises engaging a surface of the conveying belt using the motorized roller  202  to drive the conveying belt  204  via rotation of the motorized roller  202 . The conveying belt  204  is tracked around the rollers via engagement of the surface of the conveying belt with the rollers, wherein the conveying surface moves along the predetermined path, and material deposited on the conveying surface peels off of the conveying surface as the conveying belt  204  bends around the rollers on the return stretch. The substrates are removed from the conveying belt at the destination point. 
     In one embodiment, the method of conveying substrates from a starting point to a destination point along a predetermined path further comprises sweeping deposited material from the conveying surface using a cleaning brush disposed adjacent to the conveying surface at a location on the return stretch. In another embodiment, the method further comprises cooling the conveying belt using at least one cooling plate positioned between two rollers under a segment of the conveying belt opposite the conveying surface. 
       FIG. 3  is an enlarged partial side cross-sectional view of a section of one embodiment of a self cleaning belt conveyor.  FIG. 3  shows an embodiment wherein one or more of the rollers  101 ,  102 , or  103  may have one or more crowns or bumps  325  protruding from their exterior surface to assist in tracking the conveying belt (see  FIG. 3 ). 
       FIG. 4  shows another embodiment of a self cleaning belt conveyor comprising a chain driven continuous caterpillar track  431 . As shown in  FIG. 4 , the belt conveyor  400  may comprise two or more adjacent caterpillar tracks  431 . Each caterpillar track  431  may be coupled with and driven by at least two chains (only one chain is shown as  727  in  FIG. 7A ). Each chain  727  may be supported on and rotated about at least two sprockets  428  (see also  528  in  FIG. 5 ). The sprockets  428  may have teeth that engage the chain  727  as it moves about each sprocket  428 . The chain may be a commercially available attachment chain, and may be made of metal. In one example, one sprocket  428  may be attached with a portion of a drive shaft  401 , said drive shaft  401  being longitudinally parallel to, and on one side of a supporting frame  426  which may itself be supported within the chamber. Another sprocket  428  may be attached to a portion of another drive shaft  402 , said other drive shaft  402  being longitudinally parallel to, and on the opposite side of frame  426  as drive shaft  401 . Each drive shaft  401  and  402  may be supported by and rotatably coupled to the frame  426  using a coupling mechanism, such as bearings (see  730  in  FIG. 7A ). 
     Drive shafts  401  and  402  may be coupled to a motor (not shown) which may rotate each drive shaft  401  and  402  and sprocket  428 , thus driving chain  727  about sprockets  428 . The movement of chain  727  in turn moves caterpillar track  431  around drive shafts  401  and  402 . During operation of the belt conveyor  400 , sprockets  428  will move in the same direction, the direction of movement of caterpillar track  431 . For example, sprockets  428  will all rotate in a clockwise direction, or sprockets  428  will all rotate in a counter-clockwise direction, depending on the desired direction of movement of caterpillar track  431 . A tensioner (not shown) may be used to maintain proper tension in the chain  727  for constant engagement of chain  727  on sprockets  428 . 
     The embodiment of  FIG. 4  is shown more closely in  FIG. 7A . Belt conveyor  700  may include a chain-driven continuous caterpillar track  731  comprising a plurality of slats coupled with the chain  727 . The slats of caterpillar track  731  may be parallel and adjacent to one another. In one embodiment, the caterpillar track  731  may be comprised of two different types of slats, a first type of slat  729  and a second type of slat  732 . As shown in more detail in  FIG. 5 , each slat  529  (slat  729  in  FIG. 7A ) of the first type may be long and planar, with an overhang  540  at one distal end and an underhang  541  at another distal end. Each slat  529  may also have a hole  542  at each distal end to accommodate a fastening mechanism, such as a screw or rivet. Hole  542  may be located at a portion of slat  529  between overhang  540  and underhang  541 . 
     A more magnified view of the embodiment of  FIG. 7A  (albeit from a different angle) is shown in  FIG. 7B . Each link  745  of chain  727  may comprise at least two tabs  746  protruding from, and perpendicular to, each side of the link  745  (only one tab  746  for each link  745  is visible in  FIG. 7A ). Tabs  746  may be used to secure the plurality of slats of caterpillar track  731  to chain  727 . Tabs  746  may protrude from each outer face of chain  727  and may be disposed parallel to the slats  729  on caterpillar track  731  such that each underhang (see  541  in  FIG. 5 ) of each slat  729  may rest flat against a tab  746  on the side of chain  727  from which the tab  746  protrudes. Each tab  746  may have a hole  747  to accommodate a screw or rivet. Each hole  542  (see  FIG. 5 ) at each distal end of each slat  729  may correspond with a hole  747  on one tab  746  of each link  745  of chain  727  when each slat  529  is positioned over the chain  727 . In order to assemble the caterpillar track  731  of the belt conveyor  700 , one distal end of each slat  729  may be attached or secured to a tab  746  on one chain  727  using screws or rivets going through holes  542  and  747 , and the other distal end of slat  729  may be attached in the same manner to a tab  746  on a parallel chain  727 . In this manner, each slat  729  is supported on each end by a different chain  727 . 
     The second type of slat  732  may also form the caterpillar track  731  of the belt conveyor  700 . As shown in more detail in  FIG. 6 , each slat  732  (slat  632  in  FIG. 6 ) may be long and planar, similar to slat  729 , but shorter in length and with overhangs  648  at each distal end. Slat  632  may also have holes  649  at each overhang  648  to accommodate a screw  650  or rivet. Each slat  632  may have at least one raised component  633  on conveying surface  651  of slat  632  such that a glass or substrate being conveyed on caterpillar track  731  may be raised above the conveying surface  651  such as to avoid direct contact with the conveying surface  651 . In some embodiments, slat  632  may include one, two, three, or more raised components  633 , depending on the application. The raised components  633  may be disposed at different portions of slat  632  and may be spaced regularly or irregularly. The at least one raised component  633  may be an elastomeric o-ring wrapped around slat  632  at a certain point along the length of the slat  632 . Slat  632  may also have a groove to accommodate the o-ring and keep it in place. The at least one raised component  633  may also be in the form of a button or stud attached to the conveying surface  651  of the slat  632 . For example, the button or stud may be screwed into the slat  632  or adhered to the conveying surface  651 . 
     The raised component  633  may be made of silicon or an elastomer that is compatible with the process being carried out in the chamber where the belt conveyor  700  is located. It should be noted that in some embodiments, at least one slat of the first type  729  may also comprise at least one raised component on its conveying surface, similar to the raised component  633  on slat  632 , as described above. Therefore, slats  732 , or slats  729 , or both, may comprise raised components as described above. These raised components may be of the same type or different from slat to slat. For example, slats  729  may have elastomeric studs disposed thereon while slats  732  may comprise o-rings. The type, number, and location of raised components may depend on the application. 
     Each slat  732  may be positioned at intervals between slats  729 . For example, track  731  may have five consecutive slats of the first type, slat  729 , followed by one slat of the second type, slat  732 , followed by five consecutive slats of the first type, slat  729 , and so on, to form a repetitive pattern throughout track  731 , as shown in  FIG. 7A . The number, frequency and patterns of slats of the first and second type may vary, thereby forming an irregular pattern. In another embodiment, there may be ten slats of the first type in between each slat  732 , or there may be two slats of the first type in between each slat  732 . In yet another embodiment, the number of slats of the first type may vary between each slat  732 . Different combinations and patterns of types of slats  729  and  732  may be used. 
     A connector  734  may be used to couple each slat  732  to links on each chain  727  supporting track  731 . The connector  734  may be shorter in length than slat  732 , and it may have an underhang at each distal end. The connector  734  may have four holes, one at each underhang and one at each distal end between the underhangs. In this manner, each hole in the underhang may line up with a hole  649  (see  FIG. 6 ) in the overhang of slat  732  such that a screw or rivet may be used to couple slat  732  to connector  734 , as shown in  FIG. 7A . A quarter-turn quick removal screw, such as shown at  650  in  FIG. 6 , may be used to couple slat  732  to connector  734 . The two holes in between the overhangs of connector  734  may line up with holes in the two tabs  746  protruding from each link  745  of chain  727 . The connector  734  and the use of quick removal screws may allow for quick and easy removal of slat  732  for purposes of servicing, such as replacing an o-ring  733 . This may be especially useful in embodiments of belt conveyor  700  comprising more than one caterpillar track  731 . 
       FIG. 8  shows one caterpillar track  831  of a belt conveyor  800  of the embodiment as described above with respect to  FIGS. 4 and 7 . Caterpillar track  831  is supported by two pairs of sprockets  828  (back two sprockets  828  are not visible in  FIG. 8 ) coupled to shafts  801  and  802  on either side of frame  826 . The chains (such as chain  727  in  FIG. 7A ) which, according to this embodiment, would couple with each slat of caterpillar track  831  are not shown in  FIG. 8 . The caterpillar track  831  comprises two types of slats,  829  and  832 , as described above. All slats are arranged adjacent to one another, and parallel to one another and to shafts  801  and  802 . As shown in  FIG. 8 , caterpillar track  831  comprises a regular repeating pattern of five slats  829  followed by one slat  832 . In the embodiment shown in  FIG. 8 , each slat  832  comprises five evenly spaced o-rings  833  (only one exemplary o-ring is labeled in  FIG. 8 ), with each o-ring  833  secured onto each the slat  832  as described above with reference to  FIG. 7A . 
     Although  FIG. 8  shows only one caterpillar track  831 , two or more caterpillar tracks  831  may be coupled together to form a wider conveying surface, depending on the width of the glass or substrate to be transported by the belt conveyor (see  FIGS. 4 and 7 ). As described above in reference to  FIGS. 7 and 7A , in one embodiment, one caterpillar track  731  may be coupled to a chain  727  using tabs  746  protruding from one side of links  745  of chain  727 , while an adjacent caterpillar track  731  may be coupled to the same chain  727  using tabs  746  protruding from the other side of the links  745  of chain  727 . In other words, each chain  727  may be configured to support two caterpillar tracks. In this embodiment, each connector  734  may couple neighboring slats  732  on adjacent caterpillar tracks  731 . For example, connector  734  may be disposed between slats  732  on adjacent caterpillar conveyor tracks  731  such that connector  734  is coupled with a slat  732  and a tab  746  on one side of connector  734 , and a slat  732  and a tab  746  on the other side of connector  734 . Furthermore, as shown in  FIG. 7A , the overhangs of slats  729  of one caterpillar track  731  may overlap with the underhangs of slats  729  on an adjacent caterpillar track  731  such that any gaps between adjacent caterpillar tracks  731  are minimized. This reduces deposition of debris and material inside the belt conveyor  700  or on the chain  727 . Furthermore, as caterpillar track  731  bends about sprockets  728 , material deposited on the conveying surface of caterpillar track  731  may peel or flake off of the slats. In this manner, the belt conveyor may be self-cleaning. Both the raised components and the curvature of the caterpillar track  731  about the sprockets  728  may facilitate the peeling or flaking of deposited material off the conveying surface of caterpillar track  731 . The gap formed as a result of the raised component between the conveying surface and the glass or substrate being conveyed may be kept consistent because material is thus prevented from building up on the conveying surface of caterpillar track  731 . 
     The spacing between adjacent slats of caterpillar track  731  should be wide enough with respect to the pitch of chain  727  to allow caterpillar track  731  to easily move about the sprockets  728 , but narrow enough to minimize deposition of material inside of the belt conveyor  700 . 
     The frame  726  may be made of a suitable strong and corrosion resistant material, such as stainless steel. The sprockets  728  and drive shafts  801  and  802  (shown in  FIG. 8 ) may also be made of stainless steel or some other corrosion resistant material. Slats  729  and  732  should be of sufficient thickness in order to avoid wear and minimize replacements. They may be made from corrosion resistant aluminum or stainless steel, which may be electropolished to make it smooth so that material deposited on the glass or substrate being conveyed does not adhere to the conveying surface. As a result of using thicker and more process-resistant slats, the belt conveyor  700  may be operated without water cooling. However, if necessary, the belt conveyor may have a means for directing cooling fluid through drive shafts  401  and  402  (or  801  and  802 ). 
     In one embodiment, belt conveyor  700  may also comprise one or more brushes (not shown) disposed underneath a return stretch of caterpillar track  731  for sweeping deposited material or debris off the conveying surface. In one embodiment, a series of brushes may be staggered in an alternating fashion in order to obtain proper overlap between the brushes. In an alternate embodiment, belt conveyor  700  may comprise one continuous brush (not shown). 
     In another embodiment, each chain  727  may support only one caterpillar track  731  so that, in the embodiment having a plurality of caterpillar tracks  731  adjacent to one another to form a wider conveying surface, adjacent caterpillar tracks  731  are not coupled to one another, other than being driven by the same drive shafts. In this embodiment, adjacent caterpillar tracks  731  would not share the same chain or sprockets. Slats on each caterpillar track may still have underhangs and overhangs as described above so as to create overlap between slats of adjacent caterpillar tracks  731  to prevent gaps between the adjacent caterpillar tracks  731 . 
     In one embodiment, a method of conveying substrates from a starting point to a destination point along a path is provided. Referring to the embodiment of the belt conveyor illustrated in  FIGS. 4-8 , this method comprises placing one or more substrates on a belt conveyor  700 , the belt conveyor having a frame  726 , at least two motorized drive shafts (see  801  and  802  shown in  FIG. 8 ) supported by the frame  726  and connectable to a motor (not shown in  FIG. 7A ), and at least two parallel chains  727 , wherein each chain  727  is actively engaged with at least two sprockets  728  coupled with the at least two drive shafts. The belt conveyor  700  further comprises a caterpillar track  731 , wherein the caterpillar track  731  is coupled with the at least two parallel chains  727  and has a conveying surface comprising at least one raised component for supporting the substrate and wherein the caterpillar track  731  provides a substrate-conveying stretch and a return stretch. The method further comprises rotating the at least two drive shafts to move the sprockets  728 . Rotation of the at least two drive shafts and sprockets  728  will drive the at least two parallel chains  727  such that the caterpillar track  731  moves around the at least two drive shafts. The conveying surface may move along the path and material deposited on the conveying surface may peel off of the conveying surface as it moves around sprockets  728 . The substrate thereby moves on the conveying surface along the belt conveyor. The substrates may be removed from the conveying belt at the destination point. 
     The method may further comprise sweeping deposited material from the conveying surface using a cleaning brush (not shown) disposed adjacent to the conveying surface at a location on the return stretch. 
     While the embodiments of the methods of the present invention are described in accordance with the embodiments of the belt conveyors illustrated in  FIGS. 1-6 , it should be noted that the methods are not limited to the belt conveyors as illustrated in  FIGS. 1-6 , but may be used with other embodiments of belt conveyors as described above. 
     Although the invention has been described in accordance with certain embodiments and examples, the invention is not meant to be limited thereto. For instance, although some of the embodiments referred to herein describe the use of the self cleaning conveyor belt in a glass substrate processing chamber, it should be appreciated that the self cleaning conveyor belt can be used in a lower tunnel assembly as well. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.