SLIPPABLE ROLLER CONVEYOR FOR CLEAN ROOMS

Abstract: A powered conveyor (20, 120, 220) for use in a clean room environment. Objects are moved by slippable rollers (52, 152) on roller shafts (50, 150). The roller shafts (150) are driven by chain (34) and sprocket (46, 48) or by belt (224, 228) and pulley (222, 246). The driving mechanisms are contained within an enclosed volume (29, 129, 229). There is a roller shaft seal (70, 72) that retains particulate matter within the enclosure and inhibits the flow of air into the enclosure. An evacuator (30) removes air and particulates from the enclosure. The roller shafts (50) may extend across the width of the moving surface path (53), or across only a portion of the path.

Description: SLIPPABLE ROLLER CONVEYOR FOR CLEAN ROOMS BACKGROUND OF THE INVENTION Conveyors are widely used in a variety of applications for moving objects in manufacturing settings. Sometimes the manufacturing occurs within a cleanroom, in which case the objects being conveyed are sensitive to contamination. The conveyor should not threaten the object with contamination. Any contaminant generated by the conveyor should be minimized and controlled. One method of controlling contamination generated by the conveyor is to utilize a conveyor with low inherent generation of contaminants. One such type of conveyor is the type with driven, slippable rollers as described in U.S. Patent 3,951,255. These rollers rotate without slipping unless the object being conveyed stops upon encountering an obstruction. When the object stops, the rollers in contact with the object slip relative to their respective internal roller shafts and do not slip relative to the object. Thus few contaminants are generated on the object and only a limited number of rollers slip, with that slipping occuring at a roller to shaft interface that is wear resistant. Though inherently a clean type of conveyor, even a powered, slippable roller conveyor may not be clean enough for some types of cleanrooms. What is needed is a powered, slippable roller conveyor suitable for a cleanroom environment. The present invention does this in a novel and unobvious way. SUMMARY OF THE INVENTION Briefly describing one aspect of the present invention, there is provided a conveyor for moving a product along a path. The conveyor includes a first plurality of roller shafts that extend under at least a portion of the path, or that may extend completely under the path. A plurality of slippable rollers are driven by the roller shafts. A driving mechanism drives the roller shafts. The driving mechanism is largely enclosed within an enclosure, the enclosure defining an enclosed volume. The enclosure includes a two-piece resilient roller shaft seal. An evacutor removes air and particulates from the enclosed volume. In another aspect of the present invention, the two pieces of the roller shaft seal are split, with the split coinciding with a plane defined by the centerlines of the roller shafts. In another aspect of the present invention, the drive mechanism may include chains and sprockets, or pulleys and belts. In another aspect of the present invention, there may be a drive mechanism along one side of the conveyor, or there may be a drive mechanism on both sides of the conveyor. It is an object of the present invention to provide a powered conveyor with slippable rollers suitable for a clean room environment. It is another object of the present invention to make a powered conveyor with slippable rollers suitable for a clean room environment that is easy to assembly and tolerant of misalignment. These and other objects and advantages of the present invention will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of the first embodiment of the present invention. FIG. 2 is the view of FIG. 1 with parts of the driving mechanism exposed. FIG. 3 is a sectional view of FIG. 2 taken along line 3-3. FIG. 4 is an enlargement of the top portion of FIG. 3. FIG. 5 is a side view of a portion of roller shaft seal pieces 70 and 72. FIG. 6 is a view of the second embodiment of the present invention shown in a sectional view similar to the sectional view of FIG. 3. FIG. 7 is an enlargement of the top portion of FIG. 5. FIG. 8 is a depiction of the third embodiment of the present invention in a view similar to that of FIG. 6, DESCRIPTION OF THE PREFERRED EMBODIMENT For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates . The present invention relates to a powered conveyor with slippable rollers that is suitable for a clean room environment. The driving mechanisms of the conveyor are within enclosures that are evacuated. Particulate matter generated by the driving mechanisms are contained within the enclosure and ultimately evacuated from the conveyor. The evacuated particles are removed from the clean room. In this manner, a powered conveyor with slippable rollers can be operated in a clean room without violating the particulate count standards for a clean room. The present invention has four embodiments that differ in how the roller shafts are driven and whether the roller shaft span the entire moving surface path. In the first embodiment, one end of the roller shafts are driven by a chain and sprockets, and the other end of the roller shafts are rotatably received within a roller shaft support assembly on the other side of the moving surface path. In a second embodiment, the roller shafts are chain driven along each side of the moving surface path, and extend only under a portion of the surface path, leaving the center of the path relatively open. There are also third and fourth embodiments similar to the first and second. A third embodiment includes shafts driven by pulley and belt along one side of the surface path and rotatably received on the other side of the surface path. A fourth embodiment includes pulley driven shafts along each side of the surface path with the center of the path being relatively open. FIGS. 1-5 depict apparatus 20, the first embodiment of the present invention. Apparatus 20 includes conveying assembly 21, which is supported from side rail 23 by legs 24. Conveying assembly 21 includes driving assembly 22a along one side of apparatus 20 and roller shaft support assembly 22b along the other side of apparatus 20. Legs 24 also support motor and gearbox assembly 26 and evacuator 30. Motor and gearbox assembly 26 provide power to main driving sprockets 32 by a first chain (not shown) in a manner known to those of ordinary skill in the art. Sprockets 32 drive crossover shafts 42. Shafts 42 turn crossover sprockets 44. Sprockets 44 power a second chain 34 within roller driving assembly 22a. Motor assembly 26 and associated driving mechanisms are enclosed within an assembly of panels 25. Within these panels and associated seals is a first portion of a first enclosed volume 29a. The enclosure of volume 29a is relatively airtight, permitting evacuator 30 to generate a subat ospheric pressure within the first portion of volume 29a. As the driving mechanisms thus described generate particulate matter, the matter is contained within panels 25 and ultimately exhausted through nozzle 28. Nozzle 28 is typically attached to an air plenum which would further remove the particulates from the cleanroom area. Note that a separate evacuation system for the cleanroom could substitute for evacuator 30. Such a system would be attached to nozzle 28 and produce the subatmospheric pressure within volume 29a. It is preferrable if a small amount of air leaks into volume 29a. Chain 34 travels within driving assembly 22a past a series of tensioning mechanisms 36, idler sprockets 38, and oiler mechanisms 40. Chain 34 drives a plurality of outer driven sprockets 46 and inner driven sprockets 48. Sprockets 46 and 48 are attached to roller shafts 50 in an alternating manner. Roller shafts 50 drive a plurality of slippable rollers 52 in a manner described in U.S. Patent No. 3,951,255, incorporated herein by reference. The tops of rollers 52 are coincident with a surface path 53 along which objects are conveyed. A pair of bushing supports 54 rotatably receive roller shaft 50. Roller support assembly 22b rotatably receives shafts 50 in a support 54 along the side of surface path 53 opposite of driving assembly 22a. Supports 54 are attached to and supported by side rails 23. The driving mechanisms thus described for roller shafts 50 may generate particulate matter as apparatus 20 is operated. To contain particulate matter, an assembly of panels, seals, and supports enclose the driving mechanisms in a second portion of first enclosed volume 29a. The enclosure of volume 29a is relatively airtight, permitting evacuator 30 to generate a subatmospheric pressure within both the first and second portions of volume 29a. It is preferrable if a small amount of air leaks into volume 29a. Side rail member 23 is on a side of the second portion of enclosed volume 29a. Upper panel 66 and outer panel 68 are on another boundary of the second portion of volume 29a. Bottom panel 58, inner panel 60, and seal support 64 also provide boundaries to volume 29a. Seal 62 is useful in closing any gap between panels 58 and 60. A portion of roller shafts 50 are included within volume 29a. Shaft spool seal 68 rotatably receives roller shaft 50. A two piece resilient stationary roller shaft seal provides a seal between spool seal 68, panel 68, and support 64. Roller shaft seal first piece 70 contacts the upper half of spool seal 68, and is also received within a cavity formed in upper panel 66. Indentation 70a of piece 70 receives rib 66a of panel 66, and is held in place thereby. Roller shaft seal second piece 72 is in contact with the bottom half of spool seal 68 and is received within a pocket defined by seal support 64. Indentation 72a of piece 72 receives rib 64a of support 64, and is held in place thereby. Seal pieces 70 and 72 are fabricated from a resilient material such as an open cell type of cellular urethane. This resilience makes pieces 70 and 72 tolerant of misalignment of the various components of the enclosure and of the driving mechanism. First piece 70 and second piece 72 each wrap around approximately 180 degrees of spool seal 68. Semi-circular cut-outs 71 in each piece 70 and 72 are in contact with approximately half of a respective spool seal 68. Pieces 70 and 72 abut each other in the plane defined by the centerlines 73 of roller shafts 50. The width W of pieces 70 and 72 is approximately .25 inches, although the invention is not limited to this width W. This two piece, resilient construction permits easy assembly of various components onto roller shafts 50, as compared to the assembly required if pieces 70 and 72 were instead a single piece, or non resilient pieces. Pieces 70 and 72 maintain an effective air seal while being tolerant of shaft misalignment . The first and second portions of volume 29a are in fluid communication with each other. Although certain elements of the present invention have been referred to or depicted as being within either the first or second portion of volume 29a, it is understood by those of ordinary skill in the art that other combinations are encompassed by the present invention. FIGS. 6 and 7 depict apparatus 120, a second embodiment of the present invention. Apparatus 120 is similar to apparatus 20, but includes a second driving mechanism, second set of roller shafts, second set of slippable rollers, and a second enclosed volume within a second enclosure. Some of the differences between apparatus 20 and apparatus 120 will now be described. Apparatus 120 includes a conveying assembly 121 supported by legs 24. Assembly 121 includes first roller driving assembly 122a along one side of surface path 53 and second roller driving assembly 122b along the other side of surface path 53. Assembly 122b is a mirror image of assembly 122a. Within driving assembly 122b, a second set of roller shafts 150 are driven by sprockets 46 and 48. Shafts 150 are supported by bushing supports 54 and shaft restraints 154. Roller shafts 150 extend under only a portion of surface path 53. Path 53 is coincident with the tops of slippable rollers 152. Roller shafts 150 do not span the entire surface path 53 as was the case in apparatus 20. Thus, the center of apparatus 120 is open, and permits the flow of cleanroom air with little impedance. The driving mechanisms of apparatus 120 are contained within second enclosed volume 129. A first portion of first enclosed volume 129a includes within it motor 26. A second portion of first volume 129a includes within it the driving mechanisms of driving assembly 122a. First volume 129a is analgous to first enclosed volume 29a. A second enclosed volume 129b includes within it the driving mechanisms of driving assembly 122b. Volumes 129a and 129b are in fluid communication with each other, with particulate matter being removed through nozzle 28. Enclosed volume 129b and the second portion of volume 129a are defined with some of the same elements as the second portion of enclosed volume 29a. The upper boundaries of volume 129 are defined by upper panel 166, which is contained within corner panel 168 and product guide 174. Roller shaft seal first piece 70 is received within a pocket defined by upper channel 166 and retained by rib 166a. Roller shaft seal second piece 72 is received within a pocket defined by support 64. Although certain elements of the present invention have been referred to or depicted as being within either the first or second portion of volume 129a, it is understood by those of ordinary skill in the art that other combinations are encompassed by the present invention. FIG. 8 depicts apparatus 220, a third embodiment of the present invention. Apparatus 220 is similar to apparatus 120, with mirror image driving assemblies along the sides of path 53 to drive roller shafts 150 extending under only a portion of moving surface path 53. A difference between apparatus 120 and apparatus 220 is that apparatus 120 is chain-driven whereas apparatus 220 is belt-driven. Main drive pulleys 222 are driven by motor 26 (not shown). Main drive belt 224 is driven by pulley 222, and drives an intermediate pulley which is attached to drive shaft 226. Roller shaft drive belt 228 is driven by shaft 226, and in turn drives pulley 246. Pulley 246 drives roller shaft 150. Particulate matter generated by the drive mechanisms of apparatus 220 is contained within an enclosed volumes 229a and 229b. A first portion of first enclosed volume 229a includes within it motor 26, with panels 225 surrounding motor 26. A second portion of first enclosed volume 229a includes within it the driving mechanisms of driving assembly 222a. A second enclosed volume 229b includes within it the driving mechanisms of driving assembly 222b. Volumes 229a and 229b are in fluid communication. Particulate matter is ejected through nozzle 28. Although certain elements of the present invention have been referred to or depicted as being within either the first or second portion of volume 229a, it is understood by those of ordinary skill in the art that other combinations are encompassed by the present invention. Just as apparatus 220 bears similarities to apparatus 120, it is apparent to one of ordinary skill in the art that there is a fourth embodiment which is similar to apparatus 20. This fourth embodiment includes a pulley and belt driving mechanism that drives a plurality of roller shafts 50 that extend fully across and underneath surface path 53. The shafts, seals, panels, and other components of this fourth embodiment are variously described in the first, second, and third embodiments. While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

Claims: WHAT IS CLAIMED IS: 1. A conveyor for moving a product along a path, comprising : a first plurality of roller shafts extending under at least a portion of the path; a first plurality of slippable rollers driven by said first roller shafts; a first driving mechanism for driving said first roller shafts; a first enclosure of said first driving mechanism defining a first enclosed volume; and an evacuator for removing air and particulates from the enclosed volume. 2. The conveyor of claim 1 wherein said first enclosure includes a roller shaft seal comprising a first piece and a second piece, said first piece and said second piece being resilient. 3. The conveyor of claim 2 wherein one of said first piece or said second piece includes an indentation and said first enclosure includes a rib, said rib being received within said indentation for retaining said first piece or said second piece in place. 4. The conveyor of claim 2 wherein said first roller shafts have centerlines, and said first piece and said second piece abut each other in the approximate plane containing the centerlines of said first roller shafts. 5. The conveyor of claim 4 wherein said first driving mechanism includes a pulley attached to at least one of said first roller shafts and a pulley belt for driving said pulley. 6. The conveyor of claim 4 wherein said first driving mechanism includes a sprocket attached to at least one of said first roller shafts and a chain for driving said sprocket . 7. The conveyor of claim 1 further comprising: a second plurality of roller shafts extending under at least a portion of the path; a second plurality of slippable rollers driven by said second roller shafts; a second driving mechanism for driving said second roller shafts; and a second enclosure of said second driving mechanism defining a second enclosed volume. 8. The conveyor of claim 7 wherein said second enclosure includes a roller shaft seal comprising a third piece and a fourth piece, said third piece and said fourth piece being resilient. 9. The conveyor of claim 8 wherein one of said third piece or said fourth piece includes an indentation and said second enclosure includes a rib, said rib being received within said indentation for retaining said third piece or said fourth piece in place. 10. The conveyor of claim 8 wherein said second roller shafts have centerlines, and said third piece and said fourth piece abut each other in the approximate plane containing the centerlines of said second roller shafts. 11. The conveyor of claim 10 wherein said second driving mechanism includes a pulley attached to at least one of said second roller shafts and a pulley belt for driving said pulley. 12. The conveyor of claim 10 wherein said second driving mechanism includes a driven sprocket attached to at least one of said second roller shafts and a chain for driving said driven sprocket.

Inventors: STANLEY MICHAEL F, STANLEY, MICHAEL, F.
Applicants: SHUTTLEWORTH INC, STANLEY MICHAEL F, SHUTTLEWORTH, INC., STANLEY, MICHAEL, F.
Application year: 1998
Main classification: B65G13
IPC codes: B65G13, B65G23, B65G39, B65G49, F24F7