CROSS-REFERENCE TO RELATED APPLICATIONS

[0001 ] This appl ication claims priority from and the benefit of U .S. Provisional Patent Application No. 6 1 /746,60 1 , fi led December 28, 2012, entitled "CONVEYOR SYSTEM ", and which is hereby incorporated by reference.

BAC KGROU D

[0002] The present invention is directed to a conveyor system and more particularly to a roller conveyor system and various sub-assemblies thereof.

[0003] Conveyor systems are widely used within industry to transport raw materials, components and/or finished products along an assembly line or otherwise within or between manu facturing facil ities. One common conveyor system is a belt driven roller conveyor system. In belt-drive rol ler conveyor systems, a moving belt is raised or lowered beneath a set of elongated cyl inders (i .e., rol lers) to make or remove contact between the moving belt and the rol lers. When the moving belt contacts the rol lers, the rol lers rotate in the opposite d irection as the belt. As a resu lt, a bale of goods or other article situated on top of the rol lers is conveyed along the conveyor path as the rol lers rotate in place. Other roller conveyor systems are known, incl uding gravity and chain driven systems.

[0004 ] Unfortunately, numerous drawbacks are associated with conventional rol ler conveyor systems. Among those disadvantages include that the systems are often labor-intensive to instal l and maintain . Because they are often used continuously in a manufacturing or warehouse environment, rol ler conveyor systems can be subjected to long and rigorous operating cond itions, resu lting in wear and tear of components that require frequent maintenance. Maintenance of rol ler conveyor systems is often expensive, due in large part to the procurement and instal lation of spare parts, many of wh ich are heavy and cumbersome.

[0005 ] It would be desirable in the art for a rol ler conveyor system and apparatus usable for manufacturing conveyor rol lers without the above-mentioned drawbacks.

SUM MARY

[0006] One embodiment of the invention is directed to a l i fter assembly for a conveyor system including a first li fter segment, a second li fter segment and an expandable bladder in fluid communication with a pressurized fluid source. The lifter segments each have a base and an arm extending outwardly from the base and terminating at a travel stop. The arm and travel stop of each lifter segment are movably interconnected to the other l ifter segment and operable between a retracted position and an extended position. The bladder is operatively connected to the l ifter segments such that upon the bladder receiving sufficient pressurized fluid from the pressurized fl uid source for expanding the bladder and moving the lifter segments toward the extended position, one of the l ifter segments contacts and lifts a drive system into contact with conveyor rollers of the conveyor system.

[0007] Another embodiment of the invention is directed to a l ifter assembly including first and second l ifter segments movably attached to one another and defining a li fting channel having an expandable bladder contained therein. Each li fter segment has an arm extending away from a base of the li fter segment and a travel stop at a distal end of the arm. Each l i fter segment further has a keyway open ing. The keyway opening of the first li fter segment receives the arm of the second li fter segment and the keyway opening of the second lifter segment receives the arm of the first l ifter segment.

[0008] Yet another embodiment of the invention is directed to a method of assembling a lifter assembly for a conveyor system including a first lifter segment, a second l ifter segment, and an expandable bladder in flu id communication with a pressurized flu id source. The lifter segments each have a base, an arm extending outward ly from the base and terminating at a travel stop. The base of each l ifter segment includes a keyway opening extend ing to an aperture formed in the base for movably receiving the arm of the other li fter segment. The arm and travel stop of each l ifter segment are movably interconnectable relative to each other between a retracted position and an extended position. The method further includes al igning adjacent ends o the first l ifter segment and the second li fter segment and reversing the ends of the first li fter segment relative to the ends of the second li fter segment. The method further includes directing the arm of each li fter segment between the keyway opening of the other lifter segment, interconnecting the first li fter segment and the second li fter segment. The method further includes inserting the bladder in a chamber defi ned by the base and arm of each interconnected li fter segment and selectively applying pressurized fluid to the bladder.

BRI EF DESCRI PTION OF TH E FIGURES [0009] FIG. 1 shows a partial exploded view of an exemplary embodiment of a roller conveyor system .

[0010] FIG. 2 shows an isometric view of an exemplary embodiment of a bridge for a conveyor system.

[001 1 ] FIG. 3 shows an e levation view of an exemplary embodiment of a bridge for a conveyor system .

[0012] FIG. 3A-3C shows an elevation view of exemplary embodiments of a bridge for a conveyor system.

[0013] FIG. 4 shows a perspective view of an upper portion of conveyor rollers with an exemplary embodiment of bridges installed between adjacent conveyor rollers.

[0014] FIG. 5 shows an en larged elevation view of an exemplary embod iment of a bridge installed between adjacent conveyor rol lers.

[0015] FIG . 6 shows an elevation view of an exemplary embodiment of a bridge for a conveyor system.

[0016] FIG. 7 shows an isometric view of the bridge of FIG. 6.

[0017] FIG . 8Λ shows an isometric view of an exemplary embodiment of a cap for a bridge for a conveyor system .

[0018] FIG. 8B shows an opposed isometric view of the cap of FIG. 8Λ.

[0019] FIG. 9 shows an isometric view of an exemplary embodiment of a cap for a bridge for a conveyor system.

[0020] FIG. 1 0 shows a perspective view of an exemplary embodiment of a conveyor roller.

[00211 FIGS. 1 1 - 1 3 show di fferent cross-sectional views of the conveyor rol ler of FIG. 1 0.

[0022] FIG. 1 4 shows an elevation view of an exemplary conveyor rol ler.

[0023] FIG. 1 5 shows a bearing received in a conveyor rol ler. [0024] FIG. 1 6 shows an isometric view of an exemplary embodiment of a pin received in a conveyor roller.

[0025] FIG. 1 6A shows an isometric view of an exemplary embodiment of a pin received in a conveyor roller.

[0026] FIG. 1 7 shows an isometric view of an exemplary embodiment of an assembled lifter assembly.

[0027] FIG . 1 8 shows a l i fter segment of the lifter assembly of FIG. 1 7.

[0028 ] FIG . 1 9 shows a partial cutaway isometric view of an upper portion of an exemplary embodiment of a rol ler conveyor system.

[0029] FIG. 20 shows a partial cutaway elevation view of an exemplary embodiment of a roller conveyor system.

[0030] FIG. 2 1 shows a partial cutaway elevation view of the rol ler conveyor system of FIG. 20, with a li fter assembly in a retracted position.

[0031 ] FIG. 22 shows an enlarged partial cutaway elevation view of the rol ler conveyor system of FIG. 20.

[0032] FIG. 23 shows an enlarged partial cutaway elevation view of the roller conveyor system of ^' FIG . 20, except with a l i fter assembly in an extended position.

[0033 | FIGS. 24 and 24A show perspective views of exemplary embodiments of extrusion apparatus for producing a mu ltiwal l tubular structure.

[0034 ] FIG . 25 shows an elevation view of an end of exemplary embodiment of extrusion dies for produci ng a multiwal l tubular structure.

[0035] FIGS. 26A-26E show exemplary embod iments of extrusion outl ines produced by the extrusion apparatus.

[0036] FIG. 27 shows a reverse, partial cutaway view of extrusion dies of FIG. 25.

[0037] FIGS. 28A and 28B show opposed views corresponding to material entry and material exit of an apparatus for producing a multiwall tubular structure. [0038] FIG. 29 shows an enlarged, partial elevation view of extrusion dies of FIG. 25.

[0039] FIG. 30 shows a partial isometric view of extrusion dies for producing a multiwall tubular structure.

[0040] FIG. 3 1 shows a partial isometric view of an extrusion die of FIG. 30 showing flow of extrusion material.

[0041] FIG. 32 shows an elevation view of an exemplary cylindrical multiwall tubular structure produced by an extrusion apparatus of the present disclosure.

[0042] FIG. 33 shows an end view of the structure of FIG. 32.

[0043] FIG . 34 shows an isometric view of the extrusion dies of FIG. 25.

[0044] FIG. 35 shows an exploded view of the extrusion d ies of FIG. 34.

[0045] FIG. 36 shows a partial cutaway view of the extrusion dies of FIG. 34.

[0046] FIG. 37 shows an exploded view of a prior art roller assembly.

[0047] FIG. 38 shows an end view of an assembled prior art roller assembly of FIG. 37.

DETAI LED DESC RI PTION OF EXEM PLA RY EM BODI MENTS

[0048] Exemplary embodiments are directed to a conveyor system and subassemblies and components of a conveyor system that overcome drawbacks associated with such conventional systems. While discussed in the context of a particular roller conveyor system, it wi ll be appreciated that al l of the aspects of that conveyor system are not required to be used in combination. Rather any one of the components or subassemblies can be separately employed in conj unction with otherwise conventional conveyor systems or otherwise combined in any manner desired.

[0049] Exemplary embodiments are directed to an extrusion mold, to a method and apparatus, and fluid dynamic principles to enable a sel f-gu ided helical rotation, which is created when the plastic state material (at an e levated temperature) is being extruded.

[0050] Extrusion is defined as the process of shaping material, such as alum inum, by forc ing the material to flow through a shaped opening in a die. Extruded material emerges as an elongated piece of unitary construction with the same profi le as the die opening. "Plastic state" as plastic state material, as used herein is intended to encompass the condition of a material that is suitable for extrusion through the dies of the present application. For purposes o f the present application, the terms die and mandrel may be used interchangeably.

[0051 ] Turning to FIG . 1 , a roller conveyor system 1 0 constructed in accordance with exemplary embodiments is shown in schematic fashion. The roller conveyor system 1 0 inc ludes a plural ity of conveyor rollers 200 that are positioned within a frame (omitted from FIG. 1 for clarity and seen in FIG. 4) such that each rol ler can freely rotate about its axis in the absence of an appl ied braking force. It wil l be appreciated that while i l lustrated with respect to a belt-driven rol ler conveyor system 1 0, the invention is not so l imited and that one or more aspects of the invention can be used in conjunction with any suitable rol ler conveyor system such as gravity and chain driven systems, for example.

[0052] In belt-driven systems, such as the system 1 0 shown in FIG. 1 , the conveyor rol lers 200 are driven by a drive system 400 underlying the conveyor rollers 200. The drive system 400 includes a drive belt 4 10 and one or more drive rollers 420 and operates in a conventional manner. That is, power directed to the drive rol ler 420, typical ly through a motorized gear box (not shown) connected to the drive rol ler 420, causes the drive roller 420 to rotate. That, in turn, sets the drive belt 4 1 0 in motion. The drive system 400 can further include a plural ity of drive system rollers 430 that support the drive belt 4 1 0, but wh ich are not separately connected to the gear box.

[0053 ] One or more li fter assemblies 300 are positioned under the drive system 400 that raise the drive system 400 from a first, stand-by or retracted position to a second, engaged or extended position usi ng compressed air or other suitable compressed or pressurized gas from a pressurized gas source, such as a compressor 1 02 to in flate a bladder 330 attached to or otherwise arranged internal of the li fter assembly 300, as discussed in greater detail herein. When the drive belt 4 1 0 is directed into abutting contact with the rollers 200, the rollers 200 spin, causing a bale or other article situated on the rol lers to move forward in a manner consistent with conventional rol ler conveyor system operation. In another embodiment, a hydrau lic system uses a flu id (i.e., a gas and/or a liquid) as a working fluid. For purposes herein, the term gas, which includes air, and fluid (gas and/or liquid) can be used interchangeably. [0054] Although a single l i fter assembly 300 is shown in the rol ler conveyor system 1 0 of FIG. 1 , it will be appreciated that numerous lifters can be employed which can depend upon a variety of factors, including the weight of the drive system 400 being li fted, as well as other considerations such as staging and use specifications for a particular system 1 0. It wi ll further be appreciated that while the rol ler conveyor system 10 shown in FIG. 1 is a single segment, multiple segments employing multiple drive systems 400 and other components in series can be employed, depending on the total desired length of a particular rol ler conveyor system 1 0. Additional views of conveyor systems in accordance with the exemplary embodiments described herein are shown at FIGS. 19 through 22, in which the conveyor rol lers are shown situated in a frame, under which a drive system having a drive belt, drive wheel and drive rollers is positioned, with a lifter assembly in an extended configuration forcing the drive system into contact with the conveyor rollers.

[0055] In some embodiments, one or more bridges 1 00 are employed that extend the length of the rollers 200 and which provide a safe walkway for travel across the conveyor system 1 0 without otherwise impeding conveyor system operation (shown in FIG . 1 as wel l as in FIGS. 1 -22).

[0056] Turning to FIGS. 2-9. various exemplary embodiments of the bridge 1 00 are shown. As best i l lustrated in conj unction with FIGS. 2 and 3, the bridge system or bridge 1 00 includes a bridge frame 1 20 that includes a top support member 1 1 1 having an upwardly facing surface or top support surface 1 1 0 and respective fi rst and second side walls 122, 124. In one embodiment, such as shown in FIG. 2, first and second side walls 122, 124 are each joined to top support member 1 1 1 . In another embodiment, such as shown in FIG. 6, only one side wall, such as second side wal l 124 is joined to top support member 1 1 1 . The side walls are constructed with a rad ius of curvature over at least a portion of their length that substantial ly matches that of the conveyor rol lers 200 with wh ich they wi l l be employed. As i llustrated, the fi rst side wal l 122 then angles away from its adjacent roller toward, and ultimately joining, the second side wal l 1 24. I n one embodiment, an air space or hol low chamber 1 28 within the bridge 100 is thus formed that can extend the entire length of the bridge 100. The second side wall 124 extends beyond the junction point with the first side wal l 122, having a tail portion 126 that continues to fol low the curvature or substantial ly match the curvature of its adjacent rol ler 200 (best seen in FIG. 5). The length of the tail portion 126 of the second side wall 124 is such that when the bridge is inserted between two adjacent conveyor rollers 200, the tail portion 126 is at least partially beneath its adjacent roller 200. This aids in preventing the bridge 100 from popping back out during roller conveyor system operation.

[0057] The bridge frame 120 further includes a living hinge 130 extending away from the tail portion 126 of the second side wall 124 toward the opposing roller 200. The living hinge 130 is located along the tail portion 126 so that a distal end 136 of the living hinge 130 is positioned under the opposing roller 200 to further resist removal of the bridge 100. The living hinge 130 includes a notch 134 that aids in allowing the bridge system or bridge 100 to be readily inserted in the gap between two conveyor rollers 200 by application of a downward force as at least the living hinge 130 flexes at the notch 134 during insertion. That is, in one embodiment, in addition to living hinge 130 flexing at the notch 134 to facilitate insertion, a portion of tail portion 126 can also flex during insertion. The living hinge 130 resists removal in the opposite direction, because the notch 134 does not provide a predisposition for the living hinge 130 to Hex in the opposite direction. The living hinge 130 can also include a protrusion 132 formed at the distal end 136 to further resist removal of the bridge 100 during roller 200 operation.

[0058] Stated another way, as shown in FIGS.3 and 5, the bridge frame 120 includes the top support member 111 having opposed ends 112, 113, the living hinge 130 having the distal end 136, and the tail portion 126 having a distal end 127. As further shown in FIG. 5, adjacent parallel conveyor rollers 200 each have a centered longitudinal axis 202 about which the rollers 200 rotate during operation of the conveyor system. In FIG.5, longitudinal axes 202 extend in and out of the paper, appearing as points (axis 202 for single roller 200 is better shown in FIG. 10). A reference plane 204 is provided that is transverse to the longitudinal axes 202. A line 206 coincident with plane 204 passes through longitudinal axes 202 and intersects longitudinal axes 202 at intersection points 208, 209, and further intersects facing outer surface portions of the conveyor rollers at points 212, 213. Plane 204 similarly is intersected with bridge 100. yielding intersection points corresponding to opposed ends 112, 113 of top support member 111, distal end 136 of living hinge 130, and distal end 127 of tail portion 126. As further shown in FIG.5, intersection points 212, 213 of facing surfaces of adjacent parallel conveyor rollers 200 are separated by a spacing or distance 114. A spacing or distance 116 separates the distal end 136 of living hinge 130 and the distal end 127 of tail portion 126. Similarly, a spacing or distance 118 separates the opposed ends 112, 113 of top support member 111. As shown in FIG.5. since distance 116 is greater than distance 114, a downward force is needed to be applied to bridge 100 relative to the adjacent parallel rollers 200. in order to insert bridge 100 between the adjacent parallel conveyor rollers 200. In response to a downward force applied to bridge 100 relative to the adjacent parallel conveyors 200, distal end 136 of living hinge 130 is urged into elastic rotational movement 205 about the notch 134 (and also in one embodiment, a small amount of elastic deflection of distal end 127 of tail portion 126) until distance 116 is reduced until temporarily equal to distance 114, permitting distal end 136 of living hinge 130 and distal end 127 of tail portion

126 of bridge 100 to be downwardly directed between the adjacent parallel conveyor rollers 200. Once installed, the spacing between distal end 136 of living hinge 130 and distal end

127 of tail portion 126 returns to distance 116, which is greater than distance 114 between the adjacent parallel conveyor rollers 200, and since the spacing between opposed ends 112, 113 of bridge 100 is also greater than distance 114, bridge 100 is maintained in its installed position between the adjacent parallel conveyor rollers 200.

[0059] In an exemplary embodiment, the bridge 100 is sized so that the first and second side walls 122, 124 substantially match the curvature of the rollers 200 along the entire length but also sized and positioned so that the first and second side walls 122, 124 ordinarily do not contact the rollers, or are substantially maintained in a non-contacting position relative to corresponding conveyor rollers 200. The term substantially match is intended to mean that the radii of the first and second sidewalls are substantially equal to or slightly greater than the radii of the rollers along the entire longitudinal length of the rollers. In one embodiment, as generally collectively shown in FIGS.3 and 5, small portions of the upper regions of surfaces 122. 124 near ends 112. 113 of top support surface segment 111 of top support surface 110 rest in minimal areal contact with corresponding surfaces of rollers 200 by force of gravity acting on bridge 100. However, due at least to the lightweight construction of bridge 100. resistance to rotational movement of rollers 200 as a result of contact with the upper regions of surfaces 122, 124, is minimized. In another embodiment, a portion of the upper regions of surfaces 122, 124 may be constructed of or have a layer of a material having a low coefficient of friction applied thereto. This construction, or a similar construction reduces friction that must be overcome when the drive system 400 is in contact with the rollers 200 and which could cause premature wearing of the rollers and/or the bridge, as well as reduce roller speeds or increase power requirements. [0060] FIG. 4 illustrates an embodiment in which a plurality of bridges 100 have been installed side by side in a conveyor system. As further shown in FIGS.4 and 5, each bridge 100 is situated between two adjacent rollers 200, with multiple bridges 100 placed in corresponding adjacent roller gaps 203 in FIG.4. As seen in these two FIGS., the top support surface 110 of the bridge 100 lies below and is separated from the upper tangential points 201 of the conveyor rollers 200 by a distance 180. Upper tangential points 201 contact articles (not shown) that are moved by the conveyor rollers. Stated another way, maintaining the distance 180 between tangential points 201 and the top support surface 110 of the bridge 100 prevents the bridge 100 from interfering with articles, such as bales or other objects being conveyed along the rollers 200. As a result, the bridge 100 can be permanently installed in the roller conveyor system 10 rather than being inserted and removed only when crossing. As FIG.4 also reflects, it may be desirable to employ two or more bridges 100 adjacent one another which provides a wider area that can enable an individual to cross the bridge 100 more easily.

[0061] The bridge 100 can be constructed from any suitable material, but is typically polymeric, such as polypropylene, PVC, ABS or any other type of polymer that can be employed in an extrusion process by which the bridge 100 can be advantageously and economically manufactured. Other methods of manufacture include injection molding, stereo-lithography, and 3-D printing, by way of example only. To reduce weight and material cost, the bridge 100 can be formed so that it is hollow in the region between the junction of the first and second side walls 122, 124 as described above with respect to the hollow chamber 128. In that case, the bridge 100 can optionally include a cap 150 at either or both ends, as best seen in FIG.2. As shown in the more detailed view of the cap 150 in FIGS.8A and 8B, which can be manufactured by injection molding, for example, the cap 150 can be formed to attach to the bridge frame 120 via, for example, an interference fit, adhesive or other suitable method, the cap 150 being inserted at each end into the hollow chamber 128 at the end of the bridge frame 120, forming a sealed joint or fluid tight connection between caps 150 and corresponding opposed ends of bridge frame 120.

|0062] The top support surface 110 of top support member 111, designed for aiding an individual in crossing from one side of the conveyor system to the other, is typically substantially planar. However, it will be appreciated that at least a portion of the top support surface 110 can incorporate some level of texture or other nonslip feature to reduce the l ikelihood of slippage whi le walking thereon. In one embodiment, the nonsl ip feature can be a treatment of at least a portion of the top support surface of the top support member 1 1 1 , such as chemical, application of abrasive material, incorporating surface features in a mold or die. heat treatment or other suitable technique that results in surface features incorporated thereon. In one embodiment, the surface features can be a layer of nonslip material applied to at least a portion of the top support surface 1 1 0 of top support member 1 1 1 . In one embodiment, at least a portion of the top support surface 1 1 0 of top support member 1 1 1 inc ludes one or more strips 140 of a nonslip or high-tack material incorporated therein. One exemplary suitable material includes a copolymer of ethylene propylene d iene monomer (M- class) rubber, or FPDM rubber and polypropylene, commercially available under the trademark SANTOPREN E©, although any material that can provide additional traction can be employed. In some embodiments, the h igh-tack or nonsl ip strips 140 can be incorporated by being co-extruded with the bridge frame 1 20 during manufacture of the bridge 1 00 and/or through vu lcanization.

[0063] In some embodiments, the bridge 1 00 further provides a brake function or braking system or brake system 1 62. In one bridge 1 00 providing a brake function, an expandable elastic bladder 1 60 is optionally attached to the outer surface of the bridge frame, such as from one point or portion of the first side wal l 122 to another point or portion of the first side wall 1 22 (FIG. 6) and/or the living hinge 130 (FIG. 3 shows elastic bladder 160 attached to first side wall 122 and living hinge 130), form ing an air space, air chamber, brake chamber or chamber 1 68 intermediate the clastic bladder 1 60 and the bridge frame 120. In other embodiments, expandable clastic bladder 1 60 can be attached to other portions of the outer surface of the bridge frame, such as from one point or portion o f the first side wall 122 to a point or portion of the second side wall 1 24 (FIG . 3 A), or from di fferent points or portions of the second side wall 1 24 (FIG . 313), or from a point or portion of the second side wal l 1 24 to a point or portion o f the living hinge 1 30 (FIG. 3C), or any combination thereof, form ing an air space, air chamber, brake chamber or chamber 1 68.

[0064] In another embodiment, as seen in FIG. 6, a portion of the first side wal l 1 22 is partially replaced by the expandable elastic bladder 1 60 along at least a portion of the length of the bridge frame 1 20.

[0065] In either case, the elastic bladder 160 can be constructed of any rubber or other elastic material including, for example, nitrile rubber, such as that available under the trademark ALCRIN®. Like the high tack strips 140, the elastic bladder 160 can be manufactured as part of a co-extrusion process with the rest of the bridge frame 1 20, by vu lcan ization, or any other suitable method, including separate manufacture and attachment of the elastic bladder 1 60 using an adhesive, all by way of example. Furthermore, it wi l l be appreciated that whi le the elastic bladder 160 is illustrated in FIG. 6 as partial ly replacing the first side wal l 1 22, alternatively or in combination with that construction, the elastic bladder 1 60 could partially replace a portion of the second side wall 124 adjacent the opposite rol ler.

[0066] In operation, the brake system 1 62 is engaged when a pressurized gas 164 is introduced into a brake chamber or chamber 168, which can be an air space as shown in FIG. 3, hollow chamber 128 formed in the interior of the bridge frame 120 shown in FIG. 6, or any other air space enclosed by the elastic bladder 160, as it wi ll be appreciated that stil l other ways of incorporating an elastic bladder 160 into the structure of the bridge 1 00 to perform a braking function as subsequently described are also contemplated. For example, in yet another embodiment, the elastic bladder 1 60 attached to the bridge frame 120 can be an air bag in which the elastic bladder 1 60 itsel f fu l ly defines an internal volume that forms the brake chamber into which air can be introduced directly.

[0067] The term bladder as used herein is intended to include not only an elastic material that can be uti lized in combination w ith portions of the bridge frame to define an internal volume that is expandable, such as by pressurized gas, and, by virtue of a su fficient amount of such expansion, generates a braking force. The term bladder is intended to also incl ude an elastic material that by itself forms an expandable internal volume, by virtue of a sufficient amount of such expansion, generates a braking force.

[0068] The brake chamber is sealed at both ends so that when air is introduced, the increasing air pressure causes the elastic bladder 1 60 to expand, essentially expanding the effective width of the bridge 1 00 within the gap between the conveyor rollers 200 and thereby forcing the first and second bridge side walls 1 22, 124 against their respective adjacent rollers 200 to jam or prevent rotational movement of the rol lers 200 relative to the bridge 1 00. In one embodiment, the elastic bladder 1 60 extends along al l or nearly al l of the entire length of the bridge 1 00, which increases the surface area of contact achieved by the bridge 1 00 with the rollers 200. [0069] In one embodiment, introducing compressed air to achieve a pressure of about 90 psi in the hollow chamber 128 is sufficient to cause the elastic bladder 1 60 to expand about 40 to 60 mils (0.040 to 0.060 inch), which provides suffic ient contact for the braking force; in the unexpanded state (or embodiments in which an elastic bladder is not employed) a gap of about 20 mils (0.020 inch), between the rollers 200 and the first and second side walls 1 22, 1 24 is sufficient to allow the rol lers to spin freely. It will be appreciated, however, that these values are exemplary only and that any other pressures, spacings, and expanded/unexpanded distances can be used to achieve satisfactory results, which can vary based on numerous di fferent factors, including materials of construction, length, size, etc., as wel l as other aspects of particular rol ler conveyor system with which the bridge 1 00 wi ll be employed.

[0070] When the clastic bladder 1 60 is expanded, the contact force or braking force exerted by the bridge 100 along the length of the roller 200 is sufficient to prevent the roller from spinning freely. Accordingly, even i f an individual crossing the bridge 1 00 steps on the rollers 200, the brake prevents the rollers 200 from spinning in place, which can further increase safety for users as they cross the bridge 1 00. The brake system can also be employed to prevent articles from inadvertently falling forward along the roller conveyor system 1 0 by locking out the rol lers 200 and preventing "runaway" incidents.

[0071 ] Exemplary embodiments employing such a braking system significantly increase roller contact surface area and thus the braking power found in conventional braking systems which operate in a di fferent manner and further fai l to provide the dua l bene fit of ensuring a safe walking surface. In some embodiments, the braking systems can achieve as much as 4000 square inches or more of contact between the rol lers 200 and the bridge frame 1 20, although even lesser surface areas can be used to provide adequate braking power as it wi l l be appreciated that the particular area required to achieve satisfactory resu lts in any particular conveyor system wil l vary depending upon a variety of factors, including the si e of the system and the length of the bridge and/or rol lers employed.

[0072J In bridge embodiments employing a brake system, the ends of the hol low chamber 1 28 can be sealed using the end caps 1 50 previously shown and described in FIG. 8. Compressed air or other pressurized gas can be introduced into the hollow chamber 128 through a modified end cap 1 5 1 , such as one manufactured with an aperture 1 52 formed therein (shown in FIG. 9) to which a boss with a self-tapping nipple or other suitable gas inlet can be securely attached to introduce the gas, providing fluid communication between at least one end cap 1 1 and the hollow chamber 1 28. Even in embodiments employing a brake chamber di fferent from the hollow chamber 1 28 (such as those employing the design shown in FIG. 3 and air chamber 168), the hollow chamber 1 28 can still be in fluid communication with air chamber 1 68 to conveniently perm it the flow of gas thereto, the total volume of the brake chamber thus being the total volume of the hollow chamber 128 and air chamber 1 68. It wil l be appreciated that while convenient, the manner in which gas is introduced into the brake chamber is not lim ited to the ends of the bridge 1 00 and that any suitable entry point for introducing a pressurized gas, such as air or other suitable gas to the brake chamber can be employed.

(0073] In embodiments in which multiple bridges 1 00 having an elastic bladder 160 are employed adjacent one another, the compressed gas can advantageously be introduced into all of the bridges 1 00 in series via a conduit 153 (FIG. 1 ) that couples at least one other bridge 1 00, and preferably the two or more bridges 1 00 together to provide fluid communication in series between the brake chambers. I n such cases, the modi fied caps 1 5 1 of FIG. 9 can be used to close the hol low chamber 1 28 with only the final open ing in the series being the c losed cap 1 50 of F IGS. 8Λ and 8B. In other embodiments, a mani fold 1 54 (FIG. 1 ) can be used to introduce compressed air via condu its 1 53 into or otherwise interconnect the brake chambers in parallel.

[0074] Whether compressed air is introduced into the air chamber of each bridge 1 00 individual ly or into mu ltip le bridges, whether in parallel or in series, the air (or any other suitable compressed gas) can be introduced to the bridge 100 from its source, typical ly a compressor 1 02 (FIG. 1 ), using manual or automated valves to open or close the flow of compressed air into one or more of the bridges 100.

[0075] As discussed briefly, the elastic bladder 1 60 can optional ly be formed in the bridge 1 00 as part of the extrusion process during manufacture or by subsequent, separate attachment. FIG. 7 i l lustrates a view of one embodiment of a bridge frame 1 20 prior to incorporation of extruded high-tack or nonslip strips 140 or elastic bladder 1 60.

[0076] In some embodiments, a controller (not shown) can be employed for automatic brake appl ication in which the controller is in electronic communication with a sensor and one or more valves that control the flow of compressed air into the bridge 100. For example, a sensor such as an electronic eye can be used to determine when something (such as a worker or a machine) is in close proximity to the side of the system of bridges 100 or that a runaway bale is approaching. Upon the controller ^' s receipt of that signal, the controller can automatically adj ust the valves controll ing the flow of compressed air to cause the elastic bladder 1 60 to expand, and thus the brake to be appl ied, for a pre-determ ined period of time. Alternatively, the brake could be manually operated.

[0077] In either of the manual or automatic embod iments, the brake could be set up for either a continuous off or a continuous on mode as a default. In a continuous off mode, air is not directed into the brake chamber of the bridge 1 00 and the elastic bladder 1 60 is not expanded absent an affirmative act to do so. As a result, the conveyor rol lers 200 can spin freely. In one such embodiment, a sensor, such as a l ight curtain for example, can be used to automatical ly determine when the brake shou ld be appl ied (i.e., when the light curtain is broken). Conversely, in a continuous on mode as a de fault setting, air is continuously introduced into the brake chamber of the bridge 1 00 and the elastic bladder 1 60 is expanded such that the brake is constantly engaged absent a sensed signal that a product in need of conveying is approaching, for example through the use of an electron ic eye. At that point, the controller could automatical ly cut the How of gas to the brake chamber, causing the elastic bladder 1 60 to deflate and perm itting the conveyor rollers 200 to spin freely.

[0078] To further enhance the usefulness of the bridge 1 00 in manufacturing environments, it may be desirable to employ high visibility colors and/or other highly visually prominent indicia so that the bridge 100, and thus a safe crossing location, can more easi ly be identified, a feature that can also be employed with other aspects described herein. Furthermore, the bridge 1 00 (as wel l as the conveyor rol lers 200, l i fter assembly 300 and other components of the rol ler conveyor system 1 0), can be constructed o f materials that are sel f-extinguishing or contain add itives that render them as such.

[0079] ^' fuming to FIGS. 1 0- 1 3, accord ing to another exemplary embod iment, a new rol ler for use with a roller conveyor system is also provided. While described herein primari ly with respect to the conveyor rollers 200, it wi l l be appreciated that features of exemplary embodiments could also be readi ly employed for use with the drive system rol lers 430 (FIG. 1 ) of the drive system 400. The rollers, in accordance with exemplary embodiments, maximize open volume within the rol ler interior while still having sufficient strength to support the same kinds of loads experienced by conventional roller conveyer systems. [0080] Referring to FIG. 10, the conveyor roller 200 comprises a plurality of internal forms or arms 210 extending radially outward from a central core 220 toward an outer wall 230 of the roller 200. In other words, the internal forms or arms 210 are in supporting relationship with the outer wall 230. The conveyor roller 200 employs at least one. typically at least two, and in some embodiments, three or more radially outwardly extending internal forms or arms 210. The arms 210 extend axially along the length of the central core 220. The arms 210 can be axially linear or can wrap helically about the central core 220 in the axial direction.

[0081] FIGS. 11-13 illustrate cross-sectional views along the axis of the roller 200 at various radial points that illustrate helically wrapping arms 210 within the roller 200. In one embodiment, the helix angle is such that the internal form or arm 210 makes a complete rotation about the central core 220 every twelve to thirty six inches of axial roller length for a two and a half inch diameter roller, and in one embodiment the helix angle is such that the arm 210 makes a complete rotation about every twenty-four inches of axial roller length. In another embodiment, the helix angle is such that the arm 210 makes a complete rotation about every sixty inches of axial roller length. In another embodiment, the helix angle is such that the arm 210 makes a complete rotation about every eighty-four inches of axial roller length. However, it will be appreciated that the angle of the helix and thus the axial distance to achieve a full rotation of internal form or arm 210 can vary depending on a variety of factors, including the diameter of the rollers 200, the overall length of the conveyor rollers 200, the number of arms 210 and the material of construction. In some embodiments, the use of helical arms 210 within the roller 200 adds strength that distributes weight angularly about the entire circumference of the roller 200. Hxemplary embodiments may exhibit a flex modulus substantially greater than conventional steel. It will further be appreciated that one or more arms 210 can run straight without a helix depending upon the structural and strength requirements of the roller 200.

[0082] Other configurations of a conveyor roller 200 having one or more internal arms are also contemplated and can include multiple structural levels within the roller 200. Similarly, the manner in which one or more helical features are incorporated can also be varied in different embodiments.

[0083] For example, in an alternative embodiment shown in FIG. 14, an end view of a conveyor roller 200 is illustrated. In this embodiment, the roller 200 again includes a central core 220 from which forms or arms 210 extend radially outward for supporting inner wall 23 1 . In FIG. 14, the forms or arms 2 1 0 extend axially along the central core 220, but have little or no helical rotation about an axis, such as about longitudinal axis 202. In another embodiment, forms or arms 21 0 can helically rotate along longitudinal axis 202. The arms 2 10 end at an inner wall 23 1 that, like the central core 220, extends the length of the roller 200, with inner wall 23 1 surrounding central core 220. From the inner wall 23 1 , a second set of arms 21 1 extends radial ly outward toward the outer wall 230 for supporting outer wall

230, with outer wal l 230 surrounding central core 220 and inner wall 23 1 . In this embodiment, the second set of arms 2 1 1 extend axial ly between the inner and outer walls

23 1 , 230, and optional ly wrap helical ly about the axis of the rol ler 200. It wil l be appreciated that conversely the inner arms 2 1 0 could wrap helical ly about the rol ler axis wh ile the outer arms 2 1 1 are substantial ly straight. A lternatively, both sets of arms 2 1 0, 2 1 1 cou ld be hel ical and the arms could wrap in either the same or opposing directions, while in yet another embodiment, neither set of arms are helical ly rotated. As further shown in FIG. 14, both core 220 and outer wall 230 are cylindrical and centered relative to longitudinal axis 202, although in other embodiments, the core and/or outer wal l can define other geometries and/or one or both of the core and the outer wall can be non-centered for rotation relative to the rotational longitudinal axis.

[0084] It wil l thus be appreciated that a variety of different configurations can be employed in constructing a conveyor roller 200 to increase the open volume within the rol ler 200 (and thus decrease the overall weight) while still retaining sufficient strength to work for its intended purpose.

[0085] Regardless of the particular configuration, the conveyor roller 200 can be manufactured of any suitable material, includ ing aluminum, investment casting, plastic and combinations of those and other materials by way of example. I thermoplastic materials are employed, h igh strength extrudablc materials are preferred; one suitable such material includes acetal resins, but other materials may be used as wel l.

[0086] The use of an alum inum or a polymeric material provides a roller 200 that is significantly l ighter than conventional steel rollers, although the conveyor rollers 200 in accordance with exemplary embodiments sti ll retain similar strength characteristics of conventional steel rollers and can have strength properties that exceed such conventional steel rollers, including flex modulus and moment of inertia. [0087] Extrusion from plastic or aluminum can also advantageously allow the roller 200 to be manufactured as a continuous piece that can be cut to any desired roller length as it leaves the extruder, such as extruder 501 . As a result, rollers 200 can be easily manufactured to meet any desired custom conveyor width.

[0088] The rollers 200 can be of any desired diameter, although 2.5 inches and 3.5 inches are typical, which can be useful for employing the conveyor rol lers 200 of exemplary embodiments in conjunction with otherwise conventional roller conveyor systems. The wall thickness of the arms 210, central core 220, and outer wall 230 can vary depending on a variety of factors, including the size of the rol ler, material of construction, configuration, and its intended end use. In one embodiment, a thermoplastic conveyor roller 200 having the configuration shown in FIG. 1 0 and a diameter of 2.5 inches can have a wall thickness for the arms 2 1 0, central core 220 and outer wal l 230 in the range of about 0. 125 inches to 0.25 inches, whi le an aluminum conveyor roller of the same diameter can have a wall th ickness in the range of 0.060 inches to about 0.25 inches. Other wall thicknesses are contemplated and it will further be appreciated that the wall thickness of the arms 2 1 0 may not be the same as the central core 220 which can itself be the same or di fferent from the outer wal l 230. In other embodiments, wall thicknesses are contemplated that vary along the length of conveyor and/or vary as a function of the radial ly outward distance between the central core and/or inner wal l and between the inner wal l and the outer wal l.

| 0089] Returning to FIG. 1 0, the external surface of the outer wall 230 of the conveyor rol ler 200 can include a thin layer 240 of a high tack or nonsl ip material, such as SANTOPREN E®. The thickness of the high tack layer can vary, but in some embodiments is about 1 0 mi ls to about 40 mi ls (0.0 1 0 to 0.040 inch) thick. The use of a high tack layer 240 as a covering skin over the roller 200 can aid in reducing the driving force required to move the bale or other article being conveyed because of a greater friction force between it and the roller 200 by reduc ing sl ippage and by reducing sl ippage by increasing the friction between the rol ler 200 and the drive system 400 (FIG. 1 ).

[0090] Furthermore, where conveyor rollers 200 in accordance with exemplary embodiments are used in combination w ith the previously described bridge 1 00 that employs a braking system, the high tack layer 240 overlying the roller 200 can also aid in braking by increasing the friction force between the roller 200 and the first and second side walls 1 22, 1 24 of the bridge 100. It can also help to provide an additional non-skid surface to a person walking across the conveyor using the bridge; even with the use of multiple adjacent bridges 1 00, an individual' s feet are still l ikely to be in some contact with the rollers 200. The application of the thin outer layer 240 to the outer wall 230 of the roller 200 can be accompl ished through co-extrusion or any other suitable method of manufacture, such as dipping, vulcanization, powder coating, shrink wrap and epoxy, all by way of example.

[0091 ] The conveyor rollers 200 can be attached to the conveyor frame by a pin 250 (FIG. 16) or some other device that extends into, inside of or otherwise through the central core 220 of the roller 200. In some embodiments, a bearing 280 (FIG. 1 5) can be positioned within the central core 220 (best seen in FIG. 1 0) to receive the pin 250 or to separately support roller 200 by a stud, spring loaded pin. or a well or other depression formed in the frame in which the bearing 280 rests. As shown in FIG. 1 5, bearing 280 includes a plural ity of outwardly extending protrusions 282 having one or more flanges 284 extending substantial ly transverse to the protrusions 282. As further shown in FIG. 15, the combination of protrusions 282 and flanges 284 resembles a T-shape, with channels or grooves 286 providing weight savings while providing structural support. As yet further shown in FIG. 1 5, the T-shaped combination of protrusions 282 and flanges 284 extend along a hel ix relative to a longitudinal axis 288 of the bearing 280.

[0092 ] I f a pin is employed, the pin 250 can include a head 252 that can be received by the rol ler frame and that prevents the pin 250 from mov ing as the rol ler 200 rotates about it. In some embodiments, the pin 250 is formed with a hexagonal head such that the same pin 250 can be used with di fferently sized frame mountings. For example, the pin 250 can have a hexagonal head suitable for use with each of 5/8", 1 9/32 ^" and 1 1 / 1 6" frame mountings by changing the side of the head 252 on which the pin 250 is seated in the frame mounting. In other words, as shown in FIG. 16, head 252 can have opposed sides or flats, such as a hexagonal shape having three opposed sides, each opposed side having a di fferent corresponding distance 290, 291 , 292 therebetween, perm itting three different frame mounting distances. In an alternate embodiment, at least two of the opposed sides or flats are separated by a different corresponding distance.

[0093] In some embodiments, a single pin 250 extending entirely through the central core 220 of the conveyor rol ler 200 can be used. In other embodiments, two shorter pins 250 on opposing ends of the roller 200 can provide sufficient support without exhibiting sagging. [0094] The use of pins 250 having sleeve bearings 280 as axles inserted into the central core 220 of the roller 200 eliminates the need for ball bearings, a common point of failure with conventional metal rollers. The pins 250 and/or cylindrical sleeve bearings 280 can be made of any suitable material; in one embodiment, they are injection molded from a polymer such as polycarbonate or PVC material. In an embodiment, such as shown in FIG. 16A, the shaft of pin 250 is received in a sleeve 296. As further shown in FIG. 16A, the sleeve 296 includes a plurality of recesses 297 formed in the sleeve 296, resulting in an outer surface having a ribbed structure 298, saving weight while providing structural rigidity and support. The shaft of pin 250 includes a channel or groove 294 for mating with a retaining fastener 295 and retaining sleeve 296. In yet another embodiment, the pin 250 can be spring-loaded to accommodate other styles of frames on which the roller 200 is mounted.

[0095] ^' Fuming to FIGS. 17 and 18, a pneumatic lifter assembly 300 for use with a roller conveyor system 10 is illustrated. The lifter assembly 300 is constructed of two lifter segments 310a, 310b which can be identical and rotated around a longitudinal axis relative to one another. Advantageously, the lifter segments can be extruded as a continuous single length, then cut into individual lifter segments of any desired length for any particular application. In addition to pneumatics, hydraulics or other fluid systems can be used. As would be apparent to one skilled in the art, assembly of two lifter segments 310a, 310b as shown in ITG. 17 would be achieved by aligning the two lifter segments 310a, 310b, one end of lifter segment 310b then being reversed relative to lifter segment 310a, which end reversal of lifter segment 310b being combined with rotation of lifter segment 310b about an axis corresponding to the length of lifter segment 310b until corresponding keyway openings 316 (FIG. 18) are aligned with arms 312 of lifter segments 310a, 310b. Once the end of lifter segment 310b has been reversed (and rotated) relative to lifter segment 310a, each arm 312 is directed between the keyway opening of the other lifter segment, interconnecting the lifter segments 310a, 310b. To complete the assembly, a bladder 160 (FIG.22) is then inserted in a chamber 320 defined by base 317 and arm 312 of each lifter segment 310a, 310b as will be discussed in further detail below.

[0096] Referring to FIG. 18, each lifter segment 310a.310b (only lifter segment 310a shown in FIG. 18) includes an arm 312 on one end extending away from a base 317, the lifter segment 310a, and having a travel stop 314 formed at the distal end of the arm 312, or the arm 312 terminating at travel stop 314. The arm 312 and travel stop 314 typically, but not necessarily, extend the entire length of the lifter segment 310a. On a same side, but opposite end of the base 317 of lifter segment 310a. a keyway opening 316 is formed for receiving an arm 312 and travel stop 314 of an opposing lifter segment 310b. FIG. 18 shows the base 317 including apertures 318a, 318b, 318c formed therein, with reinforcing member 322 separating apertures 318a, 318b and reinforcing member 322 separating apertures 318b, 318c. Aperture 318c of each lifter segment 310a, 310b is configured to receive a corresponding travel stop 314 which is secured by the arm 312. Arm 312 is slidably movable between keyway openings 316. Apertures 318a, 318b are provided to further reduce the weight of lifter segments 310a, 310b, with reinforcing members 322, 324 providing structural support during operation of lifter assembly 300 (FIG. 17). It is to be understood that in one embodiment, aperture 318a can be the only aperture formed in base 317 and that the aperture can be sized differently. In other embodiments, there can be two or more reinforcement members subdividing aperture 318 (FIG. 17) into smaller apertures 318a, 318b, etc., and that those apertures can be sized differently. In one embodiment, instead of the travel stop, such as travel stop 314 slidably moving in a vertical direction within or inside of an aperture, such as aperture 318c, the travel stop could be exterior of the lifter segment. For example, as optionally shown in FIG. 18, a cutting line 326 can be formed in the lifter segment, resulting in a removed portion 328 from the lifter segment, leaving behind outwardly extending flanges 329 and reinforcing member 324, such that the travel stop 314 would be limited to travel between the flanges 329. However, such an arrangement may not be desirable due to an arrangement of moving parts exterior of an enclosure, such as a base.

[0097] It is to be understood that arm 312 and keyway opening 316, as well as aperture 318c and travel stop 314 are to be sized relative to one another to permit lifter segments 310a, 310b to be operatively connected therebetween for smooth operation (i.e., slidable movement of arm 312 within keyway opening 316. and slidable movement of travel stop 314 within aperture 318c; such movement occurring without binding). Such sizing must also account for the materials used, loading considerations, amount of travel required, and the like.

[0098] Returning to FIG. 17, the lifter assembly 300 is shown with both lifter segments 310a, 310b assembled having lifter segments 310a, 310b. The arms 312 of each lifter segment have been secured in the keyway opening 316 of the other lifter segment by sliding, as previously discussed. The assembled lifter segments 310a, 310b form a lifting channel or chamber 320 in the lifter assembly 300 defined by corresponding bases 317 and arms 312, with chamber 320 configured for receiving an air bladder 330 (shown in FIG. 1 and omitted here for clarity) that can be sealed at one end and connected to a compressed gas source at the other end.

[0099] As such, as shown in FIGS. 19-23, the lifter assembly 300 can be actuated between a retracted or lowered position 214 and an extended position 215, depending on whether the air bladder 330 is in a collapsed state or an expanded state, the positions 214, 215 controlled by the flow of pressurized air into the bladder. In the retracted or lowered position 214 (shown in FIG. 22), the drive belt 410 is separated from the plurality of conveyor rollers 200 by a distance 217, such that conveyor rollers 200 are free to rotate independently of the drive belt 410 (and drive system 400). In the lifter assembly's extended position 215 (shown in FIGS. 17 and 23), pressurized gas expands elastic air bladder 160, urging the lifter segment 310b into slidable vertical movement a distance 218, which distance 218 being greater than distance 217, in a direction 216 away from 310a lifter segment. As a result, the lifter segment 310b is brought into abutting contact with the frame 401 of the drive system 400 (FIG. 1), lifting the frame 401 such that belt 410 is brought into tangential contact with conveyor rollers 200 at points 219 (FIG.23). As a result, upon drive system 400 being activated such that drive belt 410 is urged into movement about drive roller 420 (FIG. 20), the conveyor rollers 200 are similarly urged into rotational movement as previously discussed.

[00100] When activation of the drive system 400 is no longer required, the flow of pressurized air can be disrupted and the amount of pressurized air in the bladder 330 is sufficiently reduced, the bladder 330 can return to its collapsed state. As a result, the lifter segment 310b returns to its retracted position 214 and the lifter segment 310b is not longer in abutting contact with the frame 401 of the drive system 400 (FIG.1). Additionally, drive belt 410 of the drive system returns to the separation distance 217 from corresponding conveyor rollers 200 (FIG.22).

[00101] Lifter assemblies in accordance with exemplary embodiments can be used to replace steel C-channel lifters used in conventional roller conveyor systems and the numerous associated drawbacks therewith, including reducing exposure of the air hose. Protecting the air hose from wear caused by the drive belt can reduce the occurrence of air line leaks, reducing operating costs and improving overall performance of the system as a whole. Lifter assemblies in accordance with exemplary embodiments also provide a bearing surface that creates less drag, further reducing energy consumption. The lifter assembly 300 can be manufactured from any suitable material, and can be of an extrudable material including aluminum or thermoplastic, making it l ightweight and further reducing energy requirements, particularly if used in conjunction with the conveyor rol lers 200 described herein.

[00102] Turning to FIGS. 24-25 and 27-36 (with FIGS. 26A-26E directed to exemplary embodiments of tubular structures that can be manufactured from an exemplary apparatus of FIGS. 24-25 and 27-36) an apparatus 500 for extruding multiwall tubular structures, such as conveyor rollers 200 having helically extending forms or arms 2 1 0 relative to a longitudinal axis 202 (FIG. 10) or drive system rollers 420 for use with a roller conveyor system 1 0 (FIG. 1 ) is i llustrated.

[00103 ] It is to be understood that such extruded multiwal l tubular structures of the present appl ication, which include helically extending arms or forms, are not lim ited to cylindrical rollers of rol ler conveyor systems, but are used in many other industries, such as vacuum cleaners to automobile transmissions of varying materials and substrates (such as alum inum, polymers, brass, lead, zinc, bronze, babbitt or bearing metal, malleable steels, alloy steels, or other suitable material for the intended application). Such helical ly extending forms can inc lude, but are not l imited to a single inside diameter (I D), multiple inside diameters (I D' s), ribs, gear teeth, bearing grooves, spl ines, fins, oi l grooves or the l ike) affixed to the outside geometry (OG) with the internal hel ical forms extending clockwise or counterclockwise along the length of the extrusion as the extrusion is formed. However, unl ike conventional multi-process procedures uti l ized in industry to provide the above-mentioned features, the extruded multiwall tubular structures, including the internal hel ical ly extending arm(s) or form(s) can be produced in a single pass extrusion. The term single pass extrusion is intended to mean that the multiwal l tubular structure, including the internal hel ically extending arm(s) or form(s) is created solely by v irtue of the plastic state material flowi ng through the dies, forming the structure, which structure is of unitary or one piece construction. Stated another way, no additional forces (axial, torsional or the like) associated with the manufacture of the structure are appl ied to the extruded structure subsequent to the structure exiting the extruder and being last contacted by the dies, such as at least one of the outer wall and the form(s) of the structure. Stated yet another way. the structure, such as at least one of the outer wall and the form(s) of the structure, lacks residual strains as a result of stress created by the manufacturing process of the structure subsequent to the structure exiting the extruder and being last contacted by the dies. For purposes herein, manufacture o f the mu ltiwall tubu lar structure subsequent to extrusion from the dies would include, for example, the application of forces resu lting in a change to the cross sectional profi le of the structure or resulting in a change in the orientation of the cross sectional profile relative to its longitudinal axis. For purposes herein, the following operations are not considered to be associated with the manufacture of the structure, such as handling or otherwise arranging the formed structure, such as for storage or shipping, cutting the structure to desired lengths, applying coatings or other surface treatments and the l ike. In one embodiment, surface texture of the multiwal l tubular structure can be achieved by the extrusion dies.

[00104] The lack of such strains, as a result of stress created by the manufacturing process of the tubular structure, subsequent to exiting the dies of the extruding apparatus of the present appl ication may result in improved material strength.

[00105] It is appreciated that extrusion apparatus 500, as generally shown in FIG. 24 includes an extruder 50 1 of known construction, which is not further d iscussed herein.

[00106] FIGS. 24 and 24Λ show one exemplary embodiment of the present appl ication, in which a die 502 is spl it or d ivided into separate pieces or portions or segments, such as die portions 502a, 502b, 502c. This exemplary embodiment is depicted in the upper two dies 502 as shown in FIG. 24 and 24A. By providing die portions 502a, 502b, 502c, nonplanar cavities or channels 503 can be machined generally longitudinally relative to the longitudinal axis 202 in adjacent facing surfaces of channels 503 of die portions 502a, 502b, 502c, perm itting the creation of helical ly extending geometries of channels 503 once die portions 502a, 502b, 502c are reassembled for production. Injection molding technology is then appl ied such that flow of plastic state material between the machined facing surfaces of channels 503 will be formed between the corresponding mandrel portions or d ie portions 502a, 502b, 502c of the extrusion die 502 in order to create extruded multiwal l tubular structures, such as conveyor rol lers 200 (e.g., FIGS. 1 0- 1 3) having forms or arms 2 1 0 extending in hel ical geometries relative to the longitudinal axis 202 ( FIGS. 1 0, 24Λ) once d ies 502 are reassembled for production. In another embodiment, two or more than three die portions may be uti l ized .

[00107| Stated another way, in an exemplary embodiment of the present application as shown in FIGS. 24 and 24A, die 502, also referred to as a split cavity die, are separated into two or more die portions (three die portions 502a, 502b, 502c are shown in one embodiment in FIGS. 24 and 24A) in such a way that opposed surfaces of the die portions can be machined in more than one plane, such that when the split cavity dies or die portions are reassembled, forming internal cavities or facing surfaces of channels 503 between adjacent die portions, a plastic state material wil l flow through the channels of the die portions during the extrusion process and continuously follow the contour of the die geometry and form a helical element within a tube or cy linder.

[00108] In another embodiment, such as further shown in FIGS. 24 and 24A. a nonplanar channel 604 is formed in a die 602, which channel 604 general ly extends along the longitudinal axis 202 of the die such that a single helically extending form is created in a multiwall tubular structure, such as similar to a single arm 2 1 0 formed in conveyor rol lers 200 (FIGS. 10- 1 3 ) as previously discussed. In other words, instead of splitting or dividing a die into multiple die portions separated by correspond ing channels, the single piece die 602 uti lizes machined nonplanar facing sides of the nonplanar channel 604 to create the helically extending arm or form. In one embodiment, more than one channel 604 is formed in die 602.

[00109] Machining of the surfaces defining a channel of the reassembled die portions or of the opposed surfaces defining a channel of a single die as shown in FIGS. 24 and 24A can be achieved by electrical discharge machining (EDM), grinding or other suitable material removal method or technique to create the nonplanar surface. In addition, suitable surface finishes for the extruded structure can be created during machining of the channel surfaces.

[001 10] For purposes o f the present appl ication, the terms die, die portion and mandrel, mandrel portion and the l ike may be used interchangeably.

[001 1 1 ] The present appl ication allows for the otherwise costly, mu lti-step, and time- consum ing process of incorporating a hel ical embodiment within a tube or cyl inder to be done in a single step via an extrusion process. Historical ly, the use of extrusion technologies to create a hel ix within a tube or cylinder has been accompl ished in a multi-phase operation. One such method uses such technology as making two separate and individual tube or cyl inder pieces and combining them together in a secondary operation.

[001 12 ] However, in addition to cost and expenditure of additional time compared to other methods, multi-step processing may have other disadvantages associated with components involving rotational movement, such as nonconcentricity, such as further discussed herein. For example, as shown in a conventional multi-step process of FIGS. 37 and 38 for respective pre-assembled and assembled conditions, a roller 700 includes a cylindrical, and preferably circular tube portion 702 having a center 704 and a longitudinal axis 706 which is coincident with center 704. As further shown in FIGS. 37 and 38. a core portion 71 2 includes a body

713 having a center 714, from which body 7 13 outwardly extend forms or arms 71 6a, 71 6b. 716c that terminate at respective ends 71 8a, 71 8b, 71 8c. As further shown in FIG. 37, once tube portion 702 and core portion 712 are axially al igned, core portion 71 2 is urged in a movement direction 720 relative to tube portion 702, which movement direction 720 being parallel to longitudinal axis 706, until core portion 71 2 is inserted inside of tube portion 702, forming roller 700.

[001 13] FIG. 38 shows an end view of the assembled roller 700 that is perpendicular to longitudinal axis 706. Assembly of tube portion 702 with core portion 712 may result in respective centers 704, 714 being m isal igned, which can also be characterized as core portion 712 being nonconcentric with tube portion 702. For example, as further shown in FIG. 38, a distance 722 between center 704 and an inner surface 708 of tube portion 702 may be greater than a distance 724 between center 714 and end 71 8a of core portion 71 2, resulting in formation of a gap 726 between end 71 8a of core portion 71 2 and inner surface 708 of tube portion 702. In order to remove gap 726, wh ich is desirable in order for form or arm 7 16a to provide structural support for tube portion 702 along end 71 8a of core portion 71 2 (and without deform ing tube portion 702), a nonconcentric distance 728 results between center

7 14 of core portion 71 2 and center 704 of tube portion 702. It is to be understood that in add ition to or alternately of gap 726, one or more of corresponding gap(s) may exist between respective ends 71 8b, 71 8c of forms or arms 71 6b, 71 6c and inner surface 708 of tube portion 702 that may result in an increase of the gap or nonconcentric distance between center 714 of core portion 71 2 and center 704 of tube portion 702.

[001 14] Conversely, a distance 722 between center 704 and inner surface 708 of tube portion 702 may be less than a distance 724' between center 7 14 and end 71 8c of core portion 7 1 2, resulting in formation o f an interference region 730 between end 7 1 8c of core portion 7 12 and inner surface 708 of tube portion 702, resulting in a movement 732. That is. for proper operation of rol ler 700, end 7 1 8c of form or arm 7 1 6c should provide structural support for tube portion 702 associated w ith interference region 730. As a result, core portion 7 12 is urged to move a distance 734 between center 714 of core portion 7 1 2 and center 704 of tube portion 702. It is to be understood that in addition to or alternately of movement 732, one or more of corresponding movement(s) may exist between respective ends 718a, 71 8b of forms or arms 716a, 716b of core portion 712 and inner surface 708 of tube portion 702 that may result in an increase of the nonconcentric distance between center 714 of core portion 712 and center 704 of tube portion 702.

[001 15] It is to be understood that one or more o f a combination of gap(s) and/or movement(s) may act between respective ends 71 8a, 7 1 8b, 71 8c of forms or arms 71 6a, 71 6b, 71 6c of core portion 71 2 and inner surface 708 of tube portion 702 to determine the nonconcentric distance between center 71 4 of core portion 7 12 and center 704 of tube portion 702. I n one embodiment, less than three forms or arms 7 1 6 may be used. In another embodiment, more than three forms or arms 71 6 may be used.

[001 16] Other methods negatively affecting alternative methods of construction may include inconsistent wall thickness of one or more of cylindrical tube portion 702 and core portion 71 2, deformation of one or more of forms or arms 71 6, and variation of curvature of the external surface of cylindrical tube portion 702, such as " flat spots".

[001 17] It is appreciated that due to the novel construction techniques associated with the present appl ication, deviations or changes of concentric ity of the resulting extrusions are prevented.

[001 18) FIG. 25 shows an assembled extrusion die set or extrusion d ie 506 comprising d ie portions 506a, 506b, 506c each including passageways 508 having receiving surfaces 5 1 0 for receiving fasteners (not shown) to secure the die portions in contact with each other. The passageways 508 shown are for receiving pins, however other suitable fasten ing arrangements such as keys, cams, taper locks, dove-tai ls or other arrangements for form ing suitable joints, threads, welds, or other su itable constructions or techniques can be uti l ized. As further shown in FIG. 25, d ie 520 is surrounded by die 506, comprising die portions 520a, 520b, 520c. As yet further shown in FIG. 25, an extrusion die set or extrusion die 522, which is surrounded by mandrel pin or die 520, optionally comprises die portions 522a, 522b, 522c. The assembled sets of dies 506, 520, 522, wh ich are general ly spaced apart from each other and in fluid communication with each other, defining an extrusion outline 524, such as shown in FIG. 25 including extrusion portions 525a, 525b, 525c that are in fluid communication with each other and can be used to create an extruded mu ltiwal l tubular structure, such as for conveyor roller 200 in FIG. 1 0 having a longitudinal axis 202. In this embodiment, extrusion portion 525b corresponds to helically extending arm or form 2 10 (FIG. 1 0). FIG. 34 shows a three-dimensional isometric view of the assembled set of extrusion dies 506, 520 and 522 and resulting extrusion outline 524.

[00119] FIG. 25 shows the outer facing of the mandrels or dies 506 corresponding to the exit point of the extruded material. In this embodiment, a center circular mandrel pin or die 522 is shown as a single piece, although die 522 can be constructed from multiple components, such as die portions 522a, 522b, 522c and of varying geometries, such as triangular, square, oval, or mu ltiple circles or geometric shapes. In one embodiment, a centered mandrel pin or die 522 cou ld be concentric re lative to the tube or cylinder to be extruded. Alternatively, the mandrel pin or die 522 could be off-center (non-concentric) or non-existent such that the hel ical ribs or elements or forms, such as extrusion portion 525b (FIG. 25) general ly extend toward each other. The internal and external components and geometries of the mandrel pin or die can be shaped to meet the needs of the end user. For each embodiment, the present application faci l itates a helical formation within a desired geometric tube or cyl inder in a single operation via an extrusion process. In one embodiment, the helical ribs or elements or forms, such as formed by extrusion portion 525b (FIG . 25) can extend into close proxim ity with each other or alternately, into contact with each other, forming a focal point. See FIGS. 26A-26E for add itional exemplary embodiments. While FIG. 26A is the on ly FIG. of FIGS. 26Λ-26Ε showing a helical element or form or arm, such as defined by extrusion portion 525b extending between an interior geometry defined by extrusion portion 525c (box) and an outer geometry defined by extrusion portion 525a, each of the other embodiments of FIGS. 26B-26E can also include a helical element or form extending between a corresponding interior geometry and exterior geometry, but are not shown for purposes of clarity. It is to be understood that other geometric arrangements incorporating one or more hel ical elements extendi ng general ly along the length of and within a tube or cylinder formed by a single-pass extrusion process fall within the scope of the present appl ication.

[00120] FIG. 27 shows a reverse, partial cutaway isometric view of extrusion dies of FIG. 25. Plastic state material wi ll be forced into the dies via an extrusion process. For purposes of clarity as to the showing of the helical geometry associated with channels 504 of extrusion portions 525b between adjacent facing die portions 520a, 520b, 520c of die 520, the length of the die portions 520a, 520b, 520c incorporating the channels 504 is shown in FIG. 27 to be longer than the die 506 (die portions 506b, 506c of die 506 are shown in FIG. 27). FIG. 35 shows a partially exploded view of the dies 506, 522, with hel ical surface 526 of die portion 520b and helical surface 528 of die portion 520c defining facing surfaces of a corresponding helical channel 504 therebetween. FIG. 36 is a reverse partial cutaway view of FIG. 35, showing hel ical surface 526 of die portion 520b (die portion 520c is not shown and a portion of die 522 is shown removed in FIG. 35). As a result of channel 504, material to be extruded is directed to flow along the helical path defined between corresponding surfaces 526 and 528 (FIG. 35).

[00121 ] FIGS. 28A and 28B show respective entry and exit views of the sets of mandrels or dies 506, 520, 522. A splitter 530, which is usable to split billets or other materials, enables the material to flow more easily and evenly with less resistance through the mandrel or die as the material is extruded. The material is then funneled into the channels 504 machined into the die portions 520a, 520b. 520c of die 520 positioned between dies 522 and 506. Die 520 is split or divided into die portions 520a, 520b, 520c in such a way as to al low the die-maker the abi l ity to machine the channels 504 of the mandrel such that the contoured channel surfaces are formed in more than one plane. Stated another way, the channel surfaces are nonplanar. This contoured nonplanar machining can be accompl ished via multiple machining processes including, but not lim ited to, electrical discharge machining (EDM), hydraulics, computerized numerical control (CNC), or conventional m i l l ing. As shown in FIGS. 27 and 35. the resulting facing surfaces defining channels 504 between correspond ing die portions 520a, 520b, 520c direct the plastic state material to flow between the nonplanar contours of the die channels and to move the material rotationally about longitudinal axis 202 of the die with the surface of the die and perpetuating this movement throughout the length of the extrusion dies. Perpetuation of such rotational movement of material is consistent with principles of fluid dynam ics, with this rotational flow of material creating the internal hel ical formation.

[00122] Whi le it may be possible to ach ieve an internally hel ical form using a die having a single channel, such as channel 604 of die 602 (FIG. 24), spl itting or div iding the die 520 into a plurality of die portions, such as three die portions 520a, 520b, 520c (FIG.27) prov ides additional structural strength and rigidity. I n add ition, use of a plural ity of die portions, such as three die portions 520a, 520b, 520c with dies 506 and 522 of FIG. 35, has been successful ly uti lized to produce an extruded multiwall tubular structure simultaneously having a plurality (3) of internal helical forms, with the tubular structure also having a uniform outer surface, in which the internal hel ical forms, and the outer surface of the extruded multiwall tubular structure are simultaneously created by the novel die construction. Uniform outer surface, such as corresponding to the resulting extruded outline defined by the outer surface of extrusion outline 524 (FIG. 25), is intended to mean that outer wall "roundness" (for a structure having a circular extrusion portion 525a as shown in FIG. 25), uniform outer wall thickness and opposed outside surface distances (the diameter for extrusion outline 524) can be satisfactori ly maintained.

[00123] FIG. 25 shows an em bodiment in which the mandre l or die 520 is split or divided into three die portions 520a, 520b, 520c. Thi s embodiment also shows machine surfaces that can be used for various purposes. For example, the channels 504 can be used to create gear teeth, heat transfer fins, bearing tracks, a sorting device, oi l grooves or other application for hel ically extend ing feature. These features can also be used to create additional drag to create concentricity and uni form ity for purposes of geometric stabi l ity of the outer tube corresponding to the cyl inder and any internal ducting of extrusion outline 524. These machining surfaces can be included in one embodiment but are not necessary in other embodiments.

[00124] FIGS. 29, 30 and 3 1 collectively, show another feature of extruder 50 1 that at least further improves the process for fabricating extruded multiwal l tubu lar structures having internal hel ical forms. That is, while the nonplanar channels 504 such as between fac ing surfaces of die portions 520a, 520b, 520c can be used to create the internal helical forms, add itional flow guiding or flow guidance features can be utilized to provide improved structures. For example, flow guiding or flow guidance features 532, such as protrusions extending radial ly outwardly along the peripheral surface of die 522 (speci fically shown in die portion 522a in FIGS. 29. 30 and 3 1 ) facing die 520, or alternately as recessed flow guidance features 534 (FIG . 29). It is to be understood that di fferent combinations of one or more recessed or protruding flow gu idance features 532, 534 can be used in di fferent embodiments. As yet further shown in FIGS. 30 and 3 1 (especial ly FIG. 3 1 ), plastic state material is urged in flow direction 536 between adjacent flow guidance features 532 between extrusion portion 525c de fined between die portions 520a. 522a. In addition, flow guidance features 532 (and/or 534) are arranged to substantial ly align with helically extending channels 504 (relative to or about longitudinal axis 202) defined by facing surfaces of the die portions of die 520 (channel 504 formed by die portions 520a, 520c are shown in FIG. 30). As used herein, substantial al ignment in the context of the channels and fluid guidance features is intended to mean the helix angle (as previously discussed) for each of the channels and fluid guidance features are substantial ly the same. In one embodiment, one or more of the guidance features can be arranged to be in radial alignment with a corresponding channel, although in another embodiment, one or more of the guidance features can be radially offset relative to the longitudinal axis.

[00125] One skil led in the art can appreciate that the flow guidance features are arranged to substantially align with channels 504 (FIG. 29) such that material flowing through extrusion portion 525a, 525b, 525c (FIG. 29) is urged to flow in How direction 536 (FIG. 3 1 ). Optionally, in one embodiment, such as further shown in FIG. 29, die 520 has a flow guidance feature 632 (shown as a recess in FIG. 29, although in another embodiment, one or more features(s) can be protrusion(s)) formed therein to help guide flow through extrusion portion 525a. In one embodiment, flow gu idance feature 632 is arranged to be substantial ly al igned with channels 504. Stated another way, as a result o f one or more of hel ically directed channels 504 and/or flow gu idance features 532 (and/or 534) and 632 (FIG. 29), extruded (plastic state) material flowing through the dies of the extrusion apparatus of the present appl ication, such as a multiwall tubular structure having core 220, at least one form or arm 2 1 0 (three arms shown in FIG. 1 0) and outer wall 230 (FIG. 1 0) are col lectively and simultaneously directed into un i form rotational movement about a longitudinal axis, such as longitudinal axis 202 as a result of the material flowing through the extrusion dies, the material last contacting the extrusion dies. That is, the structural components of the multiwall tubular structure (e.g., core 220, form or arm 2 1 0 and outer wall 230 of FIG. 1 0) as extruded by the extruder of the present appl ication each have substantially the same hel ical angle relative to or about a longitud inal axis ( longitudinal axis 202 in FIG. 1 0).

[00126] It is to be understood that for some materials, only one or more channels of the present application may be required to achieve multiwall tubular structure having internal hel ical form(s). In other embodiments, flow guidance features can be used in combination with the one or more channels for improved results, such as achiev ing one or more of more uniform wal l thickness, more uniform outer dimensions, improved strength, reduced residual stresses during manufacture due to a lack of residual stresses associated with torsional and/or axial forces applied subsequent the structure exiting the extrusion dies of the present appl ication and the l ike. The profi le of the flow guidance features as well as the channels can employ a helix angle, as previously defined, that can range widely depending upon one of more of the material to be extruded, the application of use of the extruded material, the shape of the extrusion, the number and/or shape of the flow guidance features, the desired manufacturing feed rate, and other reasons contemplated by one having ski ll in the art of material extrusion.

[00127] It is to be understood that in one embodiment different materials can be directed into the extrusion dies, such as, for example, to provide different properties to di fferent portions of the extruded structure.

[00128] FIGS 32 and 33 show an exemplary embodiment of a finished product 536 defining a tube or cyl inder having a circular core 537, an internal outwardly hel ically extending form 538 that extends between core 537 and a circular outer wal l 539. Core 537 and outer wal l 539 are concentric and centered about longitudinal axis 202. As described earl ier and shown in FIGS. 26A-26B, the finished product can take on numerous geometries, includ ing ribs and geometric shapes, and the rotation of the helix can be rotated in either a clockwise or counter-clockwise direction. Regardless of the finished appearance, the present application has provided for an internal helix to be constructed within a tube or cylinder in a single operation via an extrusion process.

[00129] In other words, apparatus of the present application can eliminate secondary operations, such as machi n ing operations to form an internal hel ix within a tube or cylinder. I nstead of a multi-stage process, an internal hel ix w ith in a tube or cylinder can be extruded in a single pass, saving time, labor, and cost. Whi le prototypes of the tool ing have been generated and development is ongoing for further smoothing the external surface, the most difficult part, that is, extruding a plastic state material such that a tube or cyl inder is formed with an internally developed helix without the need for a multi-stage process, has been achieved.

|00130] A further advantage of the extrusion apparatus, as previously discussed, is that the extruded tubular structure exiting the extrud ing apparatus, such as extrusion apparatus 500 (FIG. 24) of the present application requires no subsequent forming operations. Stated another way, the extrusion apparatus of the present appl ication directs material How such that for a multiwall tubular structure having a core having a longitudinal axis, an outer wall surrounding the core, and at least one form extending hel ically relative to the longitudinal axis and between the core and the outer wal l in supporting relationship therewith formed by the extruder or extruder apparatus or apparatus of the present application, the at least one form and the outer wall of the structure exiting the extruder is last contacted by the dies of the extruder, requiring no additional processing to produce the structure.

[00131 ] There are ways to manufacture multiwal l tubular structures with internal helical forms, but not in a single-stage or single pass process. For example, internal hel ixes can be created with a broach, cold form, dri ll ing, CNC, milling, or other machining operations subsequent to a conventional extruder. As previously mentioned, injection molding, d ie casting, and investment casting may also be employed, but are limited based on size and material constraints and are highly cost prohibitive.

[00132] Whi le the foregoing speci fication il lustrates and describes exemplary embodiments, it wi ll be understood by those ski l led in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modi fications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be l im ited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention wi l l inc lude all embodiments fal l ing w ithin the scope of the appended c laims.