WO2025117056A1

WO2025117056A1 - Dual-stacked modular roller-ball belt and conveyor

Info

Publication number: WO2025117056A1
Application number: PCT/US2024/051252
Authority: WO
Inventors: Matthew L. Fourney; Joseph F. Kovacs; Christopher B. SPICER
Original assignee: Laitram LLC
Current assignee: Laitram LLC
Priority date: 2023-11-29
Filing date: 2024-10-14
Publication date: 2025-06-05
Anticipated expiration: 2026-05-29

Abstract

A conveyor using a modular conveyor belt constructed of rows of belt modules (20) having upper roller balls (36) atop lower roller balls (38) so that as the lower roller balls rotate in one direction, the upper roller balls rotate in the opposite direction. The lower roller balls (38), which, like the upper roller balls, can rotate omnidirectionally, are caused to rotate selectively by an actuation system (92, 94, 104, 114, 120) below the belt in a carryway. The actuation system is realized by linear-motor-driven movers (94), cross belts (104, 114), or inline belts (120) having surfaces that are selectively put into contact with the lower roller balls (38) to cause them to rotate in one direction and the upper roller balls (36) to rotate in the opposite direction and move each article conveyed atop the upper roller balls (36) in a selected way.

Description

DUAL-STACKED MODULAR ROLLER-BALL BELT AND CONVEYOR

TECHNICAL FIELD

The invention relates generally to power-driven conveyors and, in particular to conveyors using modular conveyor belts with upper article-supporting roller balls in contact with lower roller balls actuated by an actuator system to selectively move articles being conveyed on the belt.

BACKGROUND

Conveyor belts that have upper article-supporting rollers sitting on lower rollers are used to divert articles toward or over one side of the belt or the other. Both the upper and lower rollers are mounted in cavities to rotate on fixed axles, which limits the angles along which articles can be diverted when the rollers are actuated to rotate.

Ball belts used to divert articles have many cavities that open onto top and bottom sides of the belt. A single spherical roller ball is received in each cavity. Salient portions of the roller ball protrude past the top and bottom sides of the belt. Because the roller balls are not mounted on axles and are free to rotate in any direction, the angles at which articles atop the roller balls can be diverted is not limited. But stopping articles atop the ball belt and diverting articles on a trajectory perpendicular to the direction of belt travel require a complex actuation system to properly cause the belt's roller balls to rotate in the direction necessary for the desired article motion.

SUMMARY

One version of a conveyor belt module embodying features of the invention comprises a module body that extends in length from a first end to a second end, in width from a first side to a second side, and in thickness from a top to a bottom and that has one or more cavities. Each cavity has a lower opening at the bottom of the module body and one or more upper openings at the top of the module body. A lower roller ball is received in each of the one or more cavities. A salient portion of the lower roller ball protrudes through the lower opening. One or more upper roller balls are received in each of the one or more cavities. A salient portion of each of the one or more upper roller balls protrudes through the one or more upper openings. The one or more upper roller balls are coupled to the lower roller ball in each of the cavities so that rotation of the lower roller ball in one direction causes the one or more upper roller balls to rotate in the opposite direction.

One version of a conveyor belt comprises a top, an opposite bottom, and a plurality of cavities. Each cavity has a lower opening at the bottom and one or more upper openings at the top. A lower roller ball received in each of the cavities has a salient portion protruding through the lower opening. One or more upper roller balls atop which articles ride are received in each of the cavities and have salient portions protruding through the one or more upper openings. The one or more upper roller balls are in contact with the lower roller ball in each of the cavities so that rotation of the lower roller ball in one direction causes the one or more upper roller balls to rotate in the opposite direction.

One version of a conveyor comprises an upper carryway, a lower return, and a conveyor belt arranged in a belt loop supported along the carryway. The conveyor belt has an article-supporting outer side and an opposite inner side bounding a belt-loop interior. A drive system drives the conveyor belt in a direction of belt travel along the carry way. The conveyor belt also includes a plurality of cavities. Each cavity has a first opening at the inner side of the belt loop and one or more second openings at the outer side. A first roller ball received in each of the cavities has a salient portion protruding through the first opening. One or more second roller balls atop which articles ride along the carryway are received in each of the cavities and have salient portions protruding through the one or more second openings. The one or more second roller balls are in contact with the first roller ball in each of the cavities so that rotation of the first roller ball in a first direction causes the one or more second roller balls to rotate in an opposite second direction. An actuation system disposed in the belt-loop interior has contact surfaces selectively movable into contact with the first roller ball in one of the cavities to cause the first roller ball to rotate in the first direction and the one or more second roller balls to rotate in the second direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top isometric view of a conveyor belt module embodying features of the invention.

FIG. 2 is a bottom isometric view of the conveyor belt module of FIG. 1.

FIG. 3 is a partly exploded bottom isometric view of the conveyor belt module of FIG. 1. FIG. 4 is a partly exploded top isometric view of the conveyor belt module of FIG. 2.

FIG. 5 is an enlarged side cross section of a portion of the module of FIG. 1 taken along lines V-V.

FIGS. 6A and 6B are top and bottom isometric views of another version of a rollerball conveyor belt module.

FIG. 7 is a bottom plan view of the belt module of FIG. 6A without roller balls installed.

FIG. 8 is front elevation view of yet another version of a roller-ball conveyor belt module.

FIG. 9 is an exploded view of the roller-ball conveyor belt module of FIG. 8.

FIG. 10A is a bottom plan view of the upper half of the module body of FIG. 9, and

FIG. 10B is a top plan view of the lower half of the module body of FIG. 9.

FIG. 11 is an isometric view of a conveyor with a conveyor belt constructed of conveyor belt modules as in FIG. 1 or FIG. 6 A or FIG. 8.

FIG. 12 is a side elevation view of the conveyor of FIG. 9.

FIG. 13 is an isometric view of a conveyor using a conveyor belt constructed of belt modules as in FIG. 1 or FIG. 6A or FIG. 8 with a perpendicular cross-belt actuation system.

FIG. 14 is an isometric view of a conveyor using a conveyor belt constructed of belt modules as in FIG. 1 or FIG. 6A or FIG. 8 with an oblique cross-belt actuation system.

FIG. 15 is an isometric view of a conveyor using a conveyor belt constructed of belt modules as in FIG. 1 or FIG. 6A or FIG. 8 with an inline-belt actuation system.

FIG. 16 is a schematic of one version of a controller for a conveyor as in FIG. 11, 13, 14, or 15.

FIG. 17 is an isometric view of a conveyor as in FIG. 11 partly cut away to show the position of wearstrips supporting the conveyor belt in the carryway.

FIG. 18 is an isometric view of a conveyor as in FIG. 13 partly cut away to show the position of wearstrips supporting the conveyor belt in the carryway.

FIG. 19 is an isometric view from a bottom perspective of a conveyor belt module usable in the conveyors of FIGS. 17 and 18.

FIG. 20 is an isometric view of a conveyor as in FIG. 11 with movers supporting the conveyor belt in the carry way. FIG. 21 is a cross section of the conveyor of FIG. 20 viewed along lines XX-XX.

DETAILED DESCRIPTION

A conveyor belt module embodying features of the invention is shown in FIGS. 1 and 2. The module 20 includes a module body 21 that extends in length from a first end 22 to an opposite second end 23, in width from a first side 24 to an opposite second side 25, and in thickness from a top 26 to a bottom 27. In this version the thickness isn't uniform. The top 26 includes a top deck 28 and protuberances 30 from the deck. So the belt module's thickness is greater at the protuberances 30.

The belt module 20 has a set of first hinge eyes 32 spaced apart laterally across the width of the module 20 along the first end 22. Second hinge eyes 33 are spaced apart laterally along the second end 23. Each of the hinge eyes 32, 33 has a laterally extending rod hole 34. A modular belt is constructed of rows of one or more side-by-side belt modules 20 linked end-to-end into an endless belt loop. The first hinge eyes 32 of a belt row are interleaved with the second hinge eyes 33 of an adjacent row. The aligned rod holes 34 of the interleaved hinge eyes 32, 33 form a lateral passageway across the width of the belt. Hinge rods received in the passageways link the rows together at hinge joints at which the conveyor belt can articulate.

Upper roller balls 36 have salient portions that protrude from the protuberances 30 at the top 26 of the module body 21 as shown in FIG. 1. In this version there are four upper roller balls 36 protruding from each protuberance 30. But versions with one or more upper roller balls 36 extending from each protuberance 30 are possible. What is also possible is a version without protuberances 30 from the deck 28. For example, the upper roller balls 36 could protrude directly from a top deck. The four upper roller balls 36 are arranged at the corners of an imaginary square. But if three or more than four upper roller balls 36 are used, they could also be positioned at the corners of imaginary regular polygons.

As shown in FIG. 2, salient portions of lower roller balls 38 protrude past the bottom 27 of the belt module 20. The lower roller balls 38 are retained in a cavity 40 by retainer rings 42. The retainer rings 42 have central openings whose diameter is less than that of the lower roller balls 38. The salient portions of the lower roller balls 38 extend through the central openings. Each retainer ring 42 is fixed in place in the module 20 by ultrasonic welding or gluing. Alternative retainer ring designs can include snap-lock structure that mates with complementary snap-lock structure on the module body 21 that allows the retainer ring to be snapped into place and unsnapped for removal.

As shown in FIGS. 3 and 4, the upper and lower roller balls 36, 38 reside in the cavities 40. Each cavity has upper openings 44 at the top 26 of the module body 21 and a lower opening 45 at the bottom 27. The cavity 40 has a lower spherical cavity segment 46 in which the lower roller ball 38 is seated and four smaller spherical cavity segments 47 in which the upper roller balls 36 are received. The upper spherical cavity segments 47 open into the lower spherical cavity segment 46. Ribs 48 on the wall structure 50 bounding the main subcavity lower the friction between the lower roller ball 38 and the wall structure. Similar ribs 49 on the inside of the retainer ring 42 also reduce friction with the lower roller ball 38.

In the version shown in FIGS. 1-4 with more upper roller balls 36 than lower roller balls 38, the diameter of the upper roller balls is less than the diameter of the lower roller balls. The module body 21 can be made of acetal or polyamide, for example. The roller balls 36, 38 can be made of rubber or polyurethane for useful frictional characteristics. But they could instead be made of polyethylene, ultra-high molecular-weight polyethylene, acetal, or polyamide overmolded with rubber or polyurethane. Another possibility is to make the lower roller balls out of a magnet material producing a magnetic field and the upper roller balls out of a ferromagnetic material attracted to the lower balls by the magnetic field. The attraction can improve contact between the upper and lower roller balls.

Further details of the cavity 40 are shown in FIG. 5. The upper roller balls 36 residing in their upper spherical cavity segments 47 are positioned atop, and coupled by direct contact with, the lower roller ball 38 in the lower spherical cavity segment 46 through windows 51. If the lower roller ball 38 is rotated in the direction of the arrow 52, the upper roller balls 36 rotate in the opposite direction 54; e.g., clockwise rotation of the lower roller ball causes the upper roller balls in contact with the lower roller to rotate counterclockwise. And because the rollers are roller balls unconfined by axles, they can rotate omnidirectionally.

Another version of a conveyor belt module with stacked roller balls is shown in FIGS. 6A and 6B. The belt module 60 differs from the belt module of FIG. 1 in that its module body 61 lacks the protuberances 30 from the deck 28 shown in FIG. 1. Instead, salient portions of upper roller balls 62 extend through upper openings 64 in a deck 66 at the top of the module body 61. A salient portion of a lower roller ball 68 protrudes through a lower opening 65 at the bottom of the module body 61. As shown in FIG. 7, with the upper and lower roller balls removed, a cavity 70 through the module body 61 extends from the lower opening at the bottom to the upper opening at the top. The lower roller ball 68 resides in a lower cavity segment, and the upper roller balls 64 reside in upper cavity segments. The upper roller balls 62 are coupled to the lower roller balls 68 in direct contact through windows 72 in each cavity 70 between the upper and lower cavity segments.

The conveyor belt module 60 can be made in various ways. One way is to mold the module body 61 around the roller balls 62, 68. Another way is to make provisions in the roller body 61 to receive retainer rings at the bottom as in the module of FIG. 2 or similarly at the top. A third way is to mold the module bottom in two halves: a top half and a bottom half. Then the roller balls 62, 68 are inserted in the resulting split cavity, and the two halves joined and welded, glued, or snapped together to retain the roller balls.

Yet another version of a conveyor belt module 55 with stacked roller balls is shown in FIGS. 8-10B. In this version the module body is composed of two halves: an upper half 56 and a lower half 57. A lower roller ball 58 and upper roller balls 59 are mounted in two cavity-halves 67, 69 that form a single cavity when the two module-body halves 56, 57 are joined. The diameter of the lower roller ball 58 is greater than the diameter of the upper roller balls 59. Also mounted in the cavity are two sets of friction-reducing rollers in the form of cylindrical wheels 71, 73 that rotate on axles. The wheels 71, 73 can be made of stainless steel or of a low-friction polymer material, such as high-density polyethylene (HDPE) or polytetrafluoroethylene (PTFE), at least on the outer surface. The first set of friction-reducing wheels 71 is positioned in the cavity in rolling contact with the lower roller ball 58 when the lower ball is raised upward by contact from below. The cavity is spacious enough for the lower roller ball 58 to fall away by gravity from contact with the first set of wheels 71. Each of the friction-reducing wheels 73 of the second set is positioned in the cavity in rolling contact with an associated upper roller ball 59. Positioned with their points of contact with the lower roller ball 58 and the upper roller balls 59 between the roller balls and walls bounding the cavity, the friction-reducing wheels 71, 73 prevent the upper and lower roller balls from rubbing against the cavity walls while the lower roller ball is being rolled, as in a trackball computer mouse. In this way the lower and upper roller balls 58, 59 can be made of a high-friction elastomeric or rubber material for non-slip contact between the lower roller balls and the upper roller balls, between the upper roller balls and conveyed articles, and between the lower roller balls and contact surfaces along a carryway. The friction-reducing rollers can alternatively be spherical rollers instead of cylindrical wheels.

FIG. 11 shows a conveyor 74 with a conveyor belt 76 constructed of conveyor belt modules as in FIG. 1 or FIG. 6A or FIG. 8. When made of such belt modules, the conveyor belt 76 is constructed of a series of rows of one or more belt modules connected end to end at hinge joints into an endless belt loop. The belt 76 is trained around drive sprockets 78 and idle rollers 79 or sprockets. A drive system including a drive motor (not shown), coupled to a drive shaft 80 on which the drive sprockets 78 are mounted, drives the belt in a direction of belt travel 82 along an upper carryway path 84. The belt 76 returns along a lower return path 85. An inner side 86 of the endless belt loop bounds a belt loop interior 88. Articles are conveyed along the carryway path 84 atop upper roller balls 90 protruding from an articlesupporting outer side 87 of the belt loop. Lower roller balls (not shown) in contact with the upper roller balls 90 protrude from the inner side 86 of the belt loop.

An actuation system that causes the upper and lower belt roller balls to rotate includes a linear-motor stator 92 and a set of linear-motor movers 94 disposed in the beltloop interior 88. (Solely for purposes of illustrating the linear-motor stator 92 and movers 94, they are shown lower than they would be in an actual conveyor system.) The linear-motor stator 92 includes an array of individually controllable coil modules along the length and across the width of stator. The linear-motor movers 94 which have flat top surfaces 95, are individually driven by the stator's coil modules. The movers 94 may be driven: (a) to move in or opposite to the direction of belt travel 82 as indicated by arrow 96; (b) to move transverse, including perpendicular, to the direction of belt travel as indicated by arrow 97; or (c) to rotate 98 about an axis 99 perpendicular to the flat top surface 95 of the mover. The stator 92 levitates the movers 94 above the stator and selectively translates or rotates them according to the desired motion of the articles to which each mover is assigned. The flat top surfaces 95 of the levitated movers 94 contact the belt's lower roller balls 91 as shown in FIG. 12. The levitation force applied by the movers 94 against the lower roller balls 91 is great enough to cause the roller balls to rotate by dint of the relative motion between the conveyor belt 76 and the movers 94. Just as rotation of the lower roller balls 91 causes the upper roller balls 90 in contact to rotate in the opposite direction, motion of the movers 94 in one direction causes the lower roller balls 91 to rotate in the opposite direction. The result is that articles 100 atop the upper roller balls 90 follow the motion of the movers 94 as indicated by the corresponding arrows 96, 97, 98.

An actuation system for a conveyor 102 as shown in FIG. 13 comprises a series of actuating cross belts 104 in a belt-loop interior 106. Each cross belt 104 is individually controllable to travel in either direction 108 perpendicular to the direction of belt travel 82 in a corresponding zone 109 of the conveyor 102. Each zone 109 corresponds to the contact area of each cross belt 104 with the conveyor belt 76. Each cross belt 104 is individually movable to selectively position its top surface 110 into or out of contact with the conveyor belt's lower roller balls 91 on the upper carryway path 84. When the cross belt 104 is raised into contact with the conveyor belt's lower roller balls 91, the article 100 on the upper belt roller balls 90 above the cross belt follow the motion of the cross belt across the conveyor belt 76 toward or off one or the other lateral side of the conveyor 102. When the cross belt 104 is lowered out of contact with the lower roller balls 91, the article 100 atop the upper roller balls 90 advances with the conveyor belt 76.

A slightly different actuation system for the conveyor belt 76 is shown in the conveyor 112 in FIG. 14. In this version the roller balls 90, 91 are actuated in the upper carry way path 84 by individually controllable transverse actuation belts 114 arranged at an oblique angle 116 to the direction of belt travel 82. In this arrangement the articles 100 also follow the transverse belts 114 contacting the belt's lower roller balls 91 supporting the articles in each corresponding zone 117 on the conveyor 112. Like the actuation system of FIG. 13, the actuation system of FIG. 14 is selectively movable to position the conveyor belt 76 into or out of contact with the conveyor belt's lower roller balls 91.

An actuation system that uses a series of individually controllable inline actuation belts 120 is shown in the conveyor 122 of FIG. 15. In this version the inline actuation belts 120 are selectively driven in a direction 124 parallel to the direction of belt travel 82 in corresponding zones 121 of the conveyor 122. As the inline actuation belt 120 in contact with the lower roller balls 91 advances in the direction of belt travel 82, the articles 100 atop the upper roller balls 90 above the inline actuation belt advance forward on the conveyor belt at the speed of the actuation belt. If, on the other hand, the actuation belt 120 advances opposite the direction of belt travel 82, the article 100 atop the upper roller balls 90 above the actuation belt follows the motion of the belt 76 rearward. And if the actuation belt 120 is stopped, the article marks time on the conveyor belt 76. In fact, for any of the actuation systems described, the articles 100 travel at the same speed and in the same direction as the actuation belts or the actuation movers.

As shown in FIG. 16, the conveyors in FIGS. 11, 13, 14, and 15 are controlled, for example, by a controller 130, such as a programmable logic controller or other programmable processor or computer, executing program steps and procedures stored in a memory to drive the movers 94 of FIG. 11 or the actuation belts 104 of FIG. 13, 114 of FIG. 14, or 120 of FIG. 15. The controller 130 receives image data from a camera 132 or other imaging device showing the location of conveyed articles on the conveyor belt. Combined with knowledge of the speed of the conveyor belt from its speed setting or from an encoder 134 or other speed-measuring device and with knowledge of the motions applied to the articles by the movers or the actuation belts, the controller 130 tracks each article on the conveyor. The controller 130 controls the speed of the conveyor belt by sending a speed signal to the conveyor belt's drive motor 136. The controller 130 controls the movers 94 of FIG. 11 by sending appropriate signals to the coil modules 138 in the linear-motor stator 92 to cause the desired article motions. Similarly, for the actuation belts 104, 114, 120 of FIGS. 13, 14, and 15, the controller 130 sends signals to the belts' drive motors 140 to cause the desired article motions.

A conveyor as in FIG. 11 is supported in the upper carry way on wearstrips 142 as shown in FIG. 17. The wearstrips 142 extend in length parallel to each other and to the direction of belt travel 82. The wearstrips 142 have support legs 144 that rest on the static linear-motor stator 92. The wearstrips 142 are received in parallel recessed lanes 146 on the inner side of the conveyor-belt loop 148. The lanes 146 are also parallel to the direction of belt travel 82 between consecutive columns of the sets 150 of upper and lower roller balls. The movers 94 are controlled by the controller 130 (FIG. 16) via the linear-motor stator 92 to avoid contact with the legs 144 by being driven under the wearstrips 142 through spaces 149 between consecutive legs. A similar wear strip arrangement is shown in FIG. 18 for use with a conveyor as in FIG. 13. Wearstrips 152 are similar to those of FIG. 17. The legs 153, however, are longer and extend through gaps 154 between adjacent actuating cross belts 104 and through open spaces 156 at the upstream side of the upstream-most actuating cross belt and at the downstream side of the downstream-most actuating cross belt. And like the wearstrips 142 of FIG. 17, the wearstrips 152 are received in the parallel recessed lanes 146 at the inner side of the conveyor-belt loop 148 to support the conveyor belt in the upper carryway.

As shown in FIG. 19, a conveyor belt module 160 usable in a conveyor as in FIG. 17 or FIG. 18 has lower protuberances 162 at the module's bottom 164. Salient portions of the lower roller balls (not shown in FIG. 19 for clarity) protrude through openings 166 in the protuberances 162. The lower protuberances 162 have side guides 168. Spaces 170 between facing side guides 168 of laterally consecutive lower protuberances 162 define the recessed lanes 146 at the inner side of the conveyor-belt loops 148 of FIGS. 17 and 18. The spaces 170 receive the wearstrips 142, 152 to support a conveyor belt constructed of rows of the belt modules 160.

The conveyor shown in FIGS. 20 and 21 uses two sets of linear-motor movers: (a) flat- top first movers (94, FIG. 11); and (b) belt supporting second movers 172. The second movers 172 support a conveyor belt 174 in a carry way without using stationary wearstrips. Instead, the second movers 172 have built-in wearstrip segments 176 that protrude upward from top sides 178 of the second movers. The wear strip segments 176 are elongated in the direction of belt travel 179 and are spaced apart a distance D precisely or roughly equal to or an integral multiple of the lateral spacing of the columns 180 of roller balls. In that way the wearstrip segments 176 can support the conveyor belt 174 in the carry way by contact with the underside of the belt between the roller-ball columns 180 when the second mover 172 is levitated against the belt by the linear-motor stator 182. To avoid collisions between the first and second movers, the linear-motor stator 182 translates the second movers 172 parallel or perpendicular to the direction of belt travel 179. When translating one of the second movers 172 perpendicular to the direction of belt travel 179, the linear-motor stator 182 lowers the second mover from contact with the underside of the conveyor belt 174 far enough to avoid contact with the roller balls. Once the translated second mover 172 is out of a first mover's trajectory and its wearstrip segments 176 are aligned with lanes 181 between adjacent roller-ball columns 180, the linear-motor stator 182 raises the second mover 172 so that its wearstrip segments 1 6 are again in contact with the underside of the conveyor belt 174 for support in the carry way.

Claims

What is claimed is:

1. A conveyor belt module comprising: a module body extending in length from a first end to a second end, in width from a first side to a second side, and in thickness from a top to a bottom and having one or more cavities, each with a lower opening at the bottom of the module body and one or more upper openings at the top of the module body; a lower roller ball received in each of the one or more cavities with a salient portion of the lower roller ball protruding through the lower opening; one or more upper roller balls received in each of the one or more cavities with a salient portion of each of the one or more upper roller balls protruding through the one or more upper openings; wherein the one or more upper roller balls are coupled to the lower roller ball in each of the cavities so that rotation of the lower roller ball in one direction causes the one or more upper roller balls to rotate in the opposite direction.

2. The conveyor belt as claimed in claim 1 wherein the one or more upper roller balls are coupled to the lower roller ball in each cavity by direct contact.

3. The conveyor belt module as claimed in claim 1 comprising a retainer ring received in the cavity at the bottom of the module body forming the lower opening and retaining the lower roller ball and the upper roller balls in the cavity.

4. The conveyor belt module as claimed in claim 1 wherein the top of the module body includes a deck and one or more protuberances from the deck and wherein the one or more upper openings are formed in the one or more protuberances.

5. The conveyor belt module as claimed in claim 1 comprising three or more upper roller balls in each cavity arranged to define corners of an imaginary regular polygon.

6. The conveyor belt module as claimed in claim 1 wherein the diameter of the upper roller balls is less than the diameter of the lower roller balls when there are multiple upper roller balls in each cavity.

7. The conveyor belt module as claimed in claim 1 wherein the lower roller balls include a magnetic material producing a magnetic field and the upper balls include a ferromagnetic material attracted to the lower roller balls by the magnetic field's interaction with the upper roller balls.

8. The conveyor belt module as claimed in claim 1 wherein the upper and lower roller balls are each made of one or another of the materials selected from the group consisting of rubber, polyurethane, rubber- or polyurethane-coated polyethylene, rubber- or polyurethane-coated ultra-high molecular-weight polyethylene, rubber- or polyurethane-coated acetal, and rubber- or polyurethane-coated polyamide.

9. The conveyor belt module as claimed in claim 1 wherein each of the one or more cavities is formed by wall structure bounding a first spherical cavity segment receiving the lower roller ball and one or more second spherical cavity segments receiving the one or more upper roller balls.

10. The conveyor belt module as claimed in claim 9 wherein the second spherical cavity segments open into the first spherical cavity segment.

11. The conveyor belt module as claimed in claim 1 wherein the module body includes a first plurality of hinge eyes spaced apart along the first end between the first and second sides and a second plurality of hinge eyes spaced apart along the second end between the first and second sides.

12. The conveyor belt module as claimed in claim 1 comprising friction-reducing rollers in each cavity contacting the upper and lower roller balls in rolling contact between the upper and lower roller balls and walls bounding the cavity.

13. The conveyor belt module as claimed in claim 12 wherein the friction-reducing rollers are made of HDPE or PTFE.

14. The conveyor belt module as claimed in claim 1 wherein the bottom of the module body includes one or more protuberances and wherein the lower opening is formed in the one or more protuberances.

15. A conveyor belt comprising: a top and an opposite bottom; a plurality of cavities formed in the conveyor belt, each cavity having a lower opening at the bottom and one or more upper openings at the top; a lower roller ball received in each of the cavities and having a salient portion protruding through the lower opening; one or more upper roller balls atop which articles ride received in each of the cavities and having salient portions protruding through the one or more upper openings; wherein the one or more upper roller balls are in contact with the lower roller ball in each of the cavities so that rotation of the lower roller ball in one direction causes the one or more upper roller balls to rotate in the opposite direction.

16. The conveyor belt as claimed in claim 15 wherein the conveyor belt comprises a plurality of conveyor belt modules hingedly linked end to end to form a conveyor belt loop.

17. The conveyor belt as claimed in claim 15 wherein the diameter of the lower roller balls is greater than the diameter of the upper roller balls.

18. The conveyor belt as claimed in claim 15 wherein the top of the conveyor belt includes a deck and a plurality of protuberances from the deck and wherein the one or more upper openings are formed in the plurality of protuberances.

19. A conveyor comprising: an upper carryway and a lower return; a conveyor belt arranged in a belt loop supported along the carryway and having an article-supporting outer side and an opposite inner side bounding a belt-loop interior; a drive system driving the conveyor belt in a direction of belt travel along the carryway; wherein the conveyor belt includes: a plurality of cavities formed in the conveyor belt, each cavity having a first opening at the inner side of the belt loop and one or more second openings at the outer side; a first roller ball received in each of the cavities and having a salient portion protruding through the first opening; one or more second roller balls atop which articles ride along the carryway received in each of the cavities and having salient portions protruding through the one or more second openings; wherein the one or more second roller balls are in contact with the first roller ball in each of the cavities so that rotation of the first roller ball in a first direction causes the one or more second roller balls to rotate in an opposite second direction; an actuation system disposed in the belt-loop interior and having contact surfaces selectively movable into contact with the first roller ball in one of the cavities to cause the first roller ball to rotate in the first direction and the one or more second roller balls to rotate in the second direction.

20. The conveyor as claimed in claim 19 wherein the actuation system comprises: a linear-motor stator including a plurality of individually controllable coil modules disposed in the belt-loop interior; a plurality of first linear-motor movers whose contact surfaces are flat top surfaces and that are individually driven by the linear-motor stator's coil modules to move in and/or transverse to the direction of belt travel and/or to rotate about an axis perpendicular to the flat top surfaces and to move into and out of contact with the first roller balls along the carryway.

21. The conveyor as claimed in claim 20 wherein each article conveyed on the conveyor belt is assignable to one of the first linear-motor movers and follows atop the second roller balls in the conveyor belt the motion of the first linear-motor mover in the belt-loop interior when the first linear-motor mover is in contact with the first roller balls.

22. The conveyor as claimed in claim 20 comprising a plurality of second linear-motor movers that include a top side and wearstrip segments extending upward from the top side and elongated in the direction of belt travel and wherein the inner side of the belt loop forms parallel lanes between the first roller balls that extend in the direction of belt travel and that are spaced to receive the wearstrip segments to support the conveyor belt on the upper carryway.

23. The conveyor as claimed in claim 19 wherein the actuation system comprises one or more cross belts selectively advanceable in a direction perpendicular to the direction of belt travel and selectively movable into and out of contact with the first roller balls to cause the articles atop the second roller balls in contact with the first roller balls to advance across the conveyor belt perpendicular to the direction of belt travel.

24. The conveyor as claimed in claim 19 wherein the actuation system comprises one or more transverse actuation belts selectively advanceable in a direction oblique to the direction of belt travel and selectively movable into and out of contact with the first roller balls to cause the articles atop the second roller balls in contact with the first roller balls to advance across the conveyor belt oblique to the direction of belt travel.

25. The conveyor as claimed in claim 19 wherein the actuation system comprises one or more inline actuation belts selectively advanceable in a direction parallel to the direction of belt travel and selectively movable into and out of contact with the first roller balls to cause the articles atop the second roller balls in contact with the first roller balls to advance parallel to the direction of belt travel at the same speed and in the same direction as the one or more inline actuation belts.

26. The conveyor as claimed in claim 19 comprising wearstrips extending in the direction of belt travel along the upper carry way and wherein the inner side of the belt loop forms parallel recessed lanes extending in the direction of belt travel and spaced to receive the wearstrips to support the conveyor belt on the upper carryway.