Short winding belt conveyor

Abstract

A belt conveyor in which a forcibly driven short pitch conveyor belt is driven about a tight conveying nose roller by a drive in which a buffer roller is positioned between the nose roller and a drive sprocket. A short take-up belt catenary depends directly from a belt release point of the sprocket to provide reverse tension to effective sprocket-belt engagement.

Description

Technical Field

[0001] The present invention relates to power driven conveyors and, more particularly, to positively driven belt conveyors having short take-up catenaries. Background Art

[0002] Unlike friction driven flat conveyor belts, positive drive conveyor belts have regularly spaced drive receiving surfaces that are engaged and driven by similarly spaced drive surfaces on a drive sprocket or drive roller slats. Positive drive conveyor belts may be homogeneous, generally flat plastic belts with regularly spaced drive receiving surfaces, or they may be modular conveyor belts constructed from rows of belt modules connected at hinged joints by hinge rods. Positive drive conveyor belts are typically driven by a drive sprocket located at the exit end of the conveyor carryway.

[0003] Belt conveyors are often used to convey products with a small footprint. However, the transfer of these products off the exit end of the belt conveyor and onto the feed end of the unloading conveyor must be tight to prevent the small footprint products from tipping over. As shown in FIG. 1 , tight transfer is achieved by positioning a small diameter nose bar or nose roller 10 at the exit end of the conveyor 12, rather than positioning a large diameter drive sprocket at the exit end of the conveyor 12. A modular conveyor belt 14 with a short pitch (the distance between consecutive drive receiving surfaces or the distance between consecutive hinge bars 16) is able to turn tightly around a small diameter nose roller 10.

[0004] As shown in FIG. 1 , the conveyor belt 14 is conventionally driven by a drive sprocket 18 positioned below the nose roller 10 and behind the nose roller 10 along the belt path. A snub roller 20 located above and behind the drive sprocket 18 is used to increase the amount of wrapping of the belt around the sprocket. After the belt 14 leaves the snub roller 20, the belt 14 forms a catenary sag in the return channel between the snub roller and a downstream return snub roller 22. The catenary sag forms a reeling area 24 of the return channel. The belt catenary in the reeling area 24 causes the length of the belt 14 to vary due to temperature, wear, and product load. Also, the weight of the belt at the catenary sag provides reverse tension directly behind the sprocket to ensure reliable sprocket-belt engagement. However, the length of the reeling area 24 in the return channel can be very long.

[0005] If the conveyor belt 14 is narrow or lightweight, the conveyor belt 14 can generate little reverse tension. In this case, the sprocket 18 cannot accelerate the belt 14 forward as fast as it should. And the situation is even worse for lightweight side-curved belts or radius belts, whose pitch changes as their rows collapse or expand. One solution is to set a counterweight take-up roller on the belt in the return channel. But many users do not like counterweight take-up rollers. Summary of the invention

[0006] One version of a belt conveyor embodying features of the invention includes: a carrying channel; a positively driven conveyor belt, the conveyor belt being driven in a direction of travel along a belt path including the carrying channel; and a nose element at an exit end of the carrying channel, about which the direction of travel of the conveyor belt changes. A drive device is disposed below the exit end and includes: a drive sprocket, the drive sprocket positively driving the conveyor belt; and a buffer roller, the buffer roller being positioned between the nose element and the drive sprocket for guiding the conveyor belt to be engaged by the drive sprocket at the top dead center of the drive sprocket.

[0007] Another type of belt conveyor includes: a conveyor belt including an outer side and an opposite inner side having a drive receiving element; a carrying channel having an exit end; and a return channel located below the carrying channel. The conveyor belt is driven along an endless belt path, the endless belt path including: a carrying channel path section along which the conveyor belt conveys articles on the outer side to the exit end along a conveying direction; a return channel path section along which the conveyor belt is driven back to the carrying channel; and a drive path section extending from the carrying channel path section at the exit end of the carrying channel to the winding path section of the return channel path section. A drive sprocket in the drive path section has a periphery with a drive element that engages with the drive receiving element on the inner side of the conveyor belt to drive the conveyor belt along the endless path. A buffer roller is located between the exit end of the carryway and the drive sprocket in the drive path section, the buffer roller contacts the outside of the conveyor belt as the conveyor belt changes direction around the buffer roller to a release point, where the conveyor belt disengages from the buffer roller at a first height. The conveyor belt is driven from the buffer roller in the drive path section to an initial engagement point on the drive sprocket at a second height. The first height is lower than the second height so that the conveyor belt travels against gravity between the buffer roller and the drive sprocket. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a side elevation view of the outlet end of a prior art belt conveyor.

[0009] Figure 2 It is a side elevation view of the outlet end of a type of belt conveyor embodying the features of the present invention.

[0010] Figure 3 It is a side elevation view of the outlet end of another type of belt conveyor embodying the features of the present invention. DETAILED DESCRIPTION

[0011] Figure 2 The exit section of a type of belt conveyor with a short wind-up and unweighted wind-up roller is shown. The belt conveyor 30 includes a forced-driven modular conveyor belt 32, which is constructed of a series of rows 34 having one or more modular belt links or modules. The rows 34 are connected together by hinge rods 36 at hinge joints 38 to form an annular loop, and the belt 32 can be hinged at the hinge joints 38. The conveyor belt 32 has an outer side 40 that supports articles and an opposite inner side 41. Drive receiving elements, such as drive dimples (not shown) are formed on the inner side 41 and are regularly spaced along the length of the belt 32. The drive receiving elements are forced to engage and drive by drive elements such as teeth 42 that are regularly spaced on the periphery of a motor-driven drive sprocket 44 that rotates in the direction of arrow 46.

[0012] The articles are conveyed along the upper carrying path 48 along the conveying direction 50 to the exit end 52 on top of the outer side 40 of the belt 32. To facilitate conveying articles with a small footprint away from the exit end 52, a nose bar or Figure 2 A small diameter nose element such as the nose roller 54 in the belt changes the direction of travel of the belt relative to the conveying direction 50.

[0013] The endless belt path consists of four main path sections: (a) a carrying channel section 56 extending from an entry end (not shown) at the beginning of the carrying channel 48 to an exit end 52; (b) a serpentine drive path section 58 on which the belt 32 engages the drive sprocket 44; (c) a return channel path section 60 located in a lower return channel 62 on which the belt returns in an inboard-upward manner toward the entry end of the conveyor 30, opposite to the conveying direction 50; and (d) a transition path section (not shown) on which the belt transitions from the lower return channel to the upper carrying channel.

[0014] Around the nose roller 54, the direction of travel of the conveyor belt 32 changes from the conveying direction 50 on the carryway section 56 to an inclined downward direction 64 on the drive path section 58. The change in direction is fixed by the position of the buffer roller 66 relative to the nose roller 54. The buffer roller 66 is positioned before the drive sprocket 44 on the drive path section 58, rather than after the drive sprocket 44. The guide surface 68 at the nose roller 54 is inclined along the direction 64. In this example, the direction of travel changes by a nose angle 70 of about 130°. However, if the serpentine drive path section is properly arranged to ensure proper sprocket-belt engagement, the nose angle may be greater than or equal to about 90°, and less than 180°.

[0015] The conveyor belt 32 travels from the nose roller 54 along an inclined downward travel direction 64 to a buffer roller 66 on the drive path section 58. Because the travel direction 64 deviates far from vertical, the conveyor belt 32 wraps around a large portion of the circumference of the buffer roller. In this example, the outer side 40 of the belt 32 contacts an arc of approximately 180° around the circumference of the buffer roller.

[0016] The height L1 of the bottom dead center 72 of the buffer roller 66 is lower than the height L2 of the top dead center 74 of the drive sprocket 44. Therefore, the conveyor belt 32 travels upwardly obliquely against gravity from the release point 76 on the buffer roller 66 to the initial engagement point 78 on the periphery of the sprocket 44. This positioning of the buffer roller 66 relative to the drive sprocket 44 increases the wrap of the belt 32 around the sprocket, thereby achieving reliable drive. The wrap of at least 135° results in effective belt-sprocket engagement.

[0017] After leaving the drive sprocket 44 at a release point 80 on the periphery of the sprocket, the belt 32 forms a catenary sag in a take-up region defined by a take-up path segment 82 located in the beginning of the return path path segment 60. The take-up region extends from the sprocket release point 80 all the way to a return roller 84 on the return path path segment 60. The top dead center 86 of the return path roller is shown as being above the bottom dead center 88 of the sprocket to help form the catenary sag and increase the amount of wrapping of the belt around the sprocket 44. The length of the take-up region is much shorter than the length of the take-up region 24 of FIG. 1. Also, because the drive sprocket 44 is pushing the belt 32 as a downward catenary, rather than upward against gravity as in FIG. 1, the belt can accelerate from a stop without disengaging from the sprockets.

[0018] Figure 3 The belt conveyor 90 shown is Figure 2The difference of the belt conveyor 30 is that the auxiliary roller 92 is positioned in the drive path section 93, between the nose roller 54 and the buffer roller 66. The auxiliary roller 92 contacts the inner side 41 of the conveyor belt 32, and the auxiliary roller 92 acts like a buffer roller of the sprocket buffer roller 66 by increasing the amount of wrapping of the belt around the buffer roller of the sprocket. The auxiliary roller 92 is used because the nose angle in this version is about 110°-20°, which is less than Figure 2 The belt conveyor 30 has a nose angle 70 of 130°. Since the belt 32 leaves the nose roller 54 in a more vertical, less inclined travel path 94, the auxiliary roller 92 changes the travel path so that the buffer roller 66 and the drive sprocket 44 can be positioned below the exit end 52 of the carrying channel 48, rather than outside the exit end, where the buffer roller 66 and the drive sprocket 44 may interfere with structures external to the belt conveyor 90. In addition, Figure 2 Belt conveyor 30 and Figure 3 The belt conveyor 90 is the same.

[0019] The short pitch conveyor belts in the exemplary form are shown and described as modular conveyor belts which may be non-collapsible straight-running conveyor belts or collapsible radius conveyor belts, but homogeneous thermoplastic conveyor belts having regularly spaced drive receiving elements and being thin enough to bend around small diameter nose bars or rollers may alternatively be used.

Claims

1. A belt conveyor, comprising: a carrying channel having an exit end; a positively driven conveyor belt, the conveyor belt being driven in a direction of travel along a belt path including the carrying channel; a nose element at the exit end of the carryway, about which the direction of travel of the conveyor belt changes; A drive device is disposed below the outlet port and comprises: a drive sprocket, the drive sprocket forcibly driving the conveyor belt and having a top dead center; A buffer roller is positioned between the nose element and the drive sprocket for guiding the conveyor belt to be engaged by the drive sprocket at the top dead center.

2. The belt conveyor according to claim 1, characterized in that: The nose element is a nose roller or a nose bar.

3. The belt conveyor according to claim 1, characterized in that: The direction of travel of the conveyor belt changes by 90° or more around the nose element.

4. The conveyor belt according to claim 3, characterized in that: The direction of travel of the conveyor belt changes by about 110° to about 130° as the conveyor belt passes around the nose element.

5. The conveyor belt according to claim 1, characterized in that: The buffer roller has a top dead point and a bottom dead point, and a height of the bottom dead point of the buffer roller is lower than a height of the top dead point of the driving sprocket.

6. The conveyor belt according to claim 5, characterized in that: The belt conveyor includes an auxiliary roller, which is arranged between the nose element and the buffer roller along the belt path for changing the travel direction of the conveyor belt on the belt path, thereby guiding the conveyor belt to contact the buffer roller at or near the top dead point of the buffer roller.

7. The conveyor belt according to claim 1, characterized in that: The buffer roller is positioned relative to the drive sprocket such that the conveyor belt travels on the belt path between the buffer roller and the drive sprocket against the force of gravity.

8. The belt conveyor according to claim 1, characterized in that: The buffer roller is positioned relative to the drive sprocket to ensure that the conveyor belt wraps around the drive sprocket through at least 135°.

9. The belt conveyor according to claim 1, characterized in that: The belt path around the buffer roller and the drive sprocket is serpentine.

10. The belt conveyor according to claim 1, characterized in that: The conveyor belt forms an endless loop having an outer side and an opposite inner side, and the buffer roller is in contact with the outer side and the drive sprocket is in positive driving engagement with the inner side.

11. The belt conveyor according to claim 1, characterized in that: The buffer roller is positioned relative to the drive sprocket to ensure that the conveyor belt initially engages the drive sprocket at an initial engagement point that is prior to the top dead center of the drive sprocket.

12. The belt conveyor according to claim 1, characterized in that: The belt conveyor includes a return roller located along the belt path after the drive sprocket, wherein the conveyor belt sags between a release point on the drive sprocket and the return roller to form a take-up region immediately after the drive sprocket.

13. A belt conveyor, comprising: a conveyor belt including an outer side and an opposing inner side having a drive receiving element; a carrying channel having an exit end; a return channel located below the carrying channel; Wherein, the conveyor belt is driven along an endless belt path, and the endless belt path includes: a carrying channel path section along which the conveyor belt conveys articles on the outer side to the exit end along a conveying direction; a return channel path segment along which the conveyor belt is driven back to the carryway, wherein the return channel path segment includes a wind-up path segment; and a drive path segment extending from the carryway path segment at the exit end of the carryway to the reel path segment of the return path path segment; a drive sprocket in the drive path section and having a periphery with drive elements that engage the drive receiving elements on the inner side of the conveyor belt to drive the conveyor belt along the endless path; a buffer roller located between the exit end of the carryway and the drive sprocket in the drive path section and contacting the outside of the conveyor belt as the conveyor belt changes direction about the buffer roller to a release point where the conveyor belt disengages from the buffer roller at a first height; wherein the conveyor belt is driven from the buffer roller to an initial engagement point on the drive sprocket at a second height in the drive path section; The first height is lower than the second height, so that the conveyor belt travels between the buffer roller and the driving sprocket against gravity.

14. The belt conveyor according to claim 13, characterized in that: The belt conveyor includes an auxiliary buffer roller on the drive path section between the buffer roller and the exit end of the carryway, the auxiliary buffer roller being positioned to divert the conveyor belt in a direction opposite to the conveying direction.

15. The belt conveyor according to claim 13, characterized in that: The belt conveyor includes an auxiliary buffer roller on the drive path section between the buffer roller and the exit end of the carryway, the auxiliary buffer roller being positioned to increase the amount of wrap of the conveyor belt around the periphery of the buffer roller compared to the amount of wrap in the absence of the auxiliary buffer roller.

16. The belt conveyor according to claim 13, characterized in that: The belt conveyor includes a nose element at the exit end of the carryway, around which the conveyor belt changes direction by an angle between about 110° and about 130° from the conveying direction along the carryway.

17. The belt conveyor according to claim 13, characterized in that: The buffer roller is positioned relative to the drive sprocket to ensure that the conveyor belt engages the drive sprocket over at least 135° of the circumference of the drive sprocket.

18. The belt conveyor according to claim 13, characterized in that: The drive path segment is serpentine.

19. The belt conveyor according to claim 13, characterized in that: The belt conveyor includes a return path roller following the drive sprocket along the belt path, wherein the conveyor belt sags between a release point on the drive sprocket and the return path roller to form the take-up path section immediately following the drive sprocket.

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