CONVEYOR WITH EDGE GUIDES

BACKGROUND OF THE INVENTION CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional application Serial No. 60/743,243, filed February 7, 2006, which is incorporated herein in its entirety.

Field of the Invention

The invention relates to a conveyor with a toothed, thermoplastic endless belt.

Description of the Related Art

Conveyors are well-known apparatuses with belts for moving objects from one location to another. Many types of conveyors are used in various industries. Examples of conveyors include conveyors with modular belts, chain belts, and endless thermoplastic belts. Some belts are more suitable for certain applications than others. For example, in the food handling industry, where a hygienic environment is critical, the thermoplastic belts are favored due to their generally continuous, smooth load-bearing or upper surface.

One type of conveyor with an endless thermoplastic belt comprises a tensioned belt having smooth upper and lower surfaces and extending between a drive pulley and a tail piece (typically a pulley or a fixed bar). Friction between the drive pulley and the belt enables transfer of torque from the former to the latter to thereby induce movement of the belt. However, friction-driven endless thermoplastic belts are still not optimal for industries such as the food industry. Because tension on the belt is required to maintain the requisite friction for moving the belt, this type of conveyor does not perform well in environments where the tension and friction can be compromised. In the food industry, introduction of grease and effluents from food products can result in a loss of friction and thereby detrimentally affect the performance of the conveyor.

Alternatively, another conveyor with an endless belt comprises a low friction, direct drive thermoplastic belt having a flat upper surface and teeth on a lower surface. This type of conveyor has the seamless flat upper surface that is easy to clean and overcomes the tension and friction problems associated with the friction driven flat belts. The teeth engage sheaves on a drive sprocket to transfer torque to the belt without requiring friction between the belt and the drive sprocket or tension in the belt. Such a conveyor is disclosed in U.S. Patent Application No. 60/593,493, which is incorporated herein by reference in its entirety.

The direct drive, toothed, endless belt conveyor can have any number of configurations, including straight, curved, inclined, or combinations thereof. One type of conveyor, which is commonly referred to as a swan neck conveyor, comprises a combination of at least one straight section and an inclined section. Often, a swan neck conveyor will have upper and lower straight sections with an intermediate inclined section. The shape of the conveyor is maintained by sidewalls that loosely guide the belt. The sidewalls, however, prevent only vertical displacement of the edges of the belt in order to maintain the desired shape; they do not prevent lateral displacement of the edges of the belt. Consequently, a common problem encountered with swan neck conveyors involves buckling of the belt at the transition between the straight and inclined sections, especially when the belt is relatively wide, on the order of about three feet wide. The side edges of the belt tend to migrate inward as the belt buckles at the transition. Furthermore, premature disengagement of the belt from the drive sprocket can also occur, which detrimentally affects the operation of the conveyor.

SUMMARY OF THE INVENTION

A conveyor having a straight section and a curved section comprises a toothed endless thermoplastic belt driven by a drive pulley. The conveyor further comprises a first guide assembly located at the juncture between straight section and the curved section to prevent buckling of an upper span of the belt. A second guide assembly located at the drive pulley also prevents buckling of the belt and prevents premature exiting of an exit tooth on the belt from an exit sheave on the drive pulley to ensure proper drive characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

Fig. 1 is a perspective view of a swan neck conveyor having a toothed, endless thermoplastic belt and guide assemblies according to one embodiment of the invention.

Fig. 2 is a plan view of a toothed surface of the belt from the conveyor shown in Fig. 1. Fig. 3 is a sectional view taken along line 3-3 of Fig. 1. Fig. 4 is a sectional view taken along line 4-4 of Fig. 1. Fig. 5 is a sectional view taken along line 5-5 of Fig. 4. Fig. 6 is a sectional view taken along line 6-6 of Fig. 1.

Fig. 7 is a perspective view of a straight conveyor having a toothed, endless thermoplastic belt and guide assemblies according to one embodiment of the invention.

DETAILED DESCRIPTION

An embodiment of a swan neck conveyor according to one aspect of the invention is shown in Figs. 1-6 and provides an endless conveyor belt and a guide assembly that prevents buckling of the belt at the juncture between straight and inclined sections of the conveyor and also at a drive pulley.

Referring now to the drawings, Fig. 1 illustrates a conveyor 10 having a straight section 12 and an inclined section 14. A belt 16 of the conveyor 10 wraps around a drive pulley 18 and an idler or slave pulley 20, with each of the pulleys 18, 20 mounted for rotation on a respective central shaft 22, 24. Sidewalls (not shown) direct the belt and maintain the shape of the straight and inclined sections 14, 16. In the illustrated embodiment, the drive and idler pulleys 18, 20 are sprockets comprising a plurality of teeth and sheaves, and each of the drive and idler pulleys 18, 20 comprise a plurality of individual pulleys spaced from one another along the respective shaft

22, 24. However, it is within the scope of the invention for the drive and idler pulleys 18, 20 to be any of a number of different forms and sizes. The pulleys 18, 20 are described in more detail below. In the illustrated configuration, a portion of the belt 16 that travels from the idler pulley 20 to the drive pulley 18 as the belt 16 travels in the direction of the arrow 26 defines a load- bearing or upper span 28 of the belt 16, and a portion of the belt 16 that travels from the drive pulley 18 to the idler pulley 20 defines a return or lower span 30 of the belt 16.

The belt 16 comprises (in the upper span 28) an upper or outside surface 32 and a lower or inside surface 34 joined along side edges 36, 38. The distance between the upper and lower surfaces 32, 34 defines a thickness of the belt 16. The upper surface 32 is fairly smooth and free of discontinuities and is typically made of a thermoplastic material, such as Pebax® resin, polyester, or polyurethane. Although not shown in the figures, the upper surface 32 can include various features, such as cleats, to facilitate the transporting of goods on the conveyor 10. As shown in Fig. 2, which is a view of the lower surface 34 of the belt 16, the distance between the side edges 36, 38 defines a lateral width of the belt 16. An exemplary lateral width for the current embodiment of the belt 16 is about thirty-six inches.

With continued reference to Fig. 2, the belt 16 has a plurality of longitudinally spaced teeth 40 on the lower surface 34. Each of the teeth 40 comprises a plurality of teeth portions 42 extending at least partly across the lateral width of the belt 16 and laterally spaced from one another by gaps 44. In the illustrated embodiment, the teeth portions 42 include a center tooth portion 42A generally wider than and located between edge teeth portions 42B located adjacent the belt side edges 36, 38. Each edge tooth portion 42B has a surface 43 facing and partly defining the gap 44. Thus, the gaps 44 between the teeth portions 42 are spaced from the corresponding belt side edge 36, 38 by at least a distance equal to the width of one of the edge teeth portions 42B. Additionally, the gaps 44 of adjacent teeth 40 are longitudinally aligned with one another in an orientation generally parallel to the belt side edges 36, 38, as are the faces 43 of the corresponding edge tooth portions 42B. The teeth portions 42 and the gaps 44 can have any suitable dimensions. For example, for the exemplary belt width of about thirty-six inches, each of the edge teeth portions 42B can have a lateral width of about one-half inch.

Furthermore, each of the teeth 40 comprises a driving face 46 and an opposite non-driving face 48.

Referring now to the longitudinal sectional view of Fig. 3, the teeth 40 of the belt 16 have a pitch P _be it defined as the distance between the centerlines of adjacent teeth 40. The belt pitch Pbeit is measured along a belt pitch line 50, which corresponds to the neutral bending axis of the belt 16. As the belt 16 bends around the pulley 18 or 20, the neutral bending axis is the imaginary plane on one side of which the belt material is under compression and on the other side of which the belt material is under tension.

The terms "upper" and "lower" refer to the opposing surfaces of the belt 16 and are used to differentiate the surface 32 upon which loads are carried and the surface 34 that has the teeth 40. It is apparent in Fig. 1 that the load-bearing surface 32 is not always the "upper" surface, and the toothed surface 34 is not always the "lower" surface, such as for the return span 30. However, for the upper span 28, the load-bearing surface 32 is usually the "upper" surface, and the toothed surface 34 is the "lower" surface. Thus, for convenience, the terms "upper" and "lower" are used to describe the surfaces 32, 34.

The drive pulley 18 and the idler pulley 20 will be described with respect to the drive pulley 18, with it being understood that the idler pulley 20 can be identical to the drive pulley 18, as shown in Fig. 1, or can differ from the drive pulley 18. Referring again to Fig. 3, the drive pulley 18 comprises a plurality of radially extending teeth 60 spaced from one another by sheaves 62. Each of the sheaves 62 has a driving face 64 and an opposed, non-driving face 66. The sheaves 62 of the drive pulley 18 have a pitch P _pu iiey defined as the arc length between centerlines of adjacent sheaves 62, measured along a pulley pitch circle 52. The pulley pitch circle 52 in this case corresponds to the belt pitch line 50 as the belt 16 wraps around the pulley 18. In other words, the pulley pitch circle 52 has the same radius as the belt pitch line 50 as the belt 16 wraps around the pulley 18.

To drive the belt 16, the sheaves 62 on the drive pulley 18 engage the belt teeth 40 to transfer torque from the drive pulley 18 to the belt 16. To achieve desired drive characteristics, it has been determined that the belt tooth pitch Pbeit is less than the drive pulley sheave pitch

P _pu ii _e y at less than maximum elongation of the belt 16. Moreover, to ensure that the belt teeth 40 are positioned to enter the drive pulley sheaves 62, the longitudinal width of each sheave 62 in the drive pulley 18 exceeds the longitudinal width of each belt tooth 40 at least by the amount of distance generated by elongating the belt 16 the maximum allowable amount over the span of the belt wrap. As a result of the pitch and width differences, the teeth 40 and the sheaves 62 are longitudinally aligned as long as the belt elongation is at or below the maximum elongation.

Due to the pitch difference between the belt 16 and the drive pulley 18, only one of the belt teeth 40 will be driven by the drive pulley 18 at any given moment. The driven tooth is an exit tooth 70, which is the tooth that is about to exit the drive pulley 18, particularly from a corresponding exit sheave 72 on the drive pulley 18. For all subsequent belt teeth 40 that enter the drive pulley sheaves 62 at any given moment, there is a gap 74 between the driving face 46 of the belt tooth 40 and the driving face 64 of the drive pulley sheave 62, and the gap 74 progressively increases in size for each successive tooth away from the driven or exit tooth 70. Consequently, as the exit tooth 70 disengages from the drive pulley 18, the gap 74 remains between the following belt tooth, i.e., a trailing tooth 76, and the driving face 64 of its respective drive pulley sheave, i.e., a trailing sheave 78. At this time, the drive pulley 18 continues to rotate relative to the belt 16 without moving the belt 16, and the effective drive characteristics are lost until the driving face 64 of the trailing sheave 78 abuts the driving face 46 of the trailing tooth 76. In other words, the drive pulley 18 rotates while the belt 16 slips until the engagement between the driving faces 64, 46 of the tailing sheave 78 and trailing tooth 76. Discounting any momentum of the belt 16 and any friction between the belt 16 and the drive pulley 18, the belt 16 will effectively stop for a brief moment until the trailing sheave driving face 64 abuts the trailing tooth driving face 46, whereby the trailing tooth 76 and the trailing sheave 78 become the new "exit tooth" and new "exit sheave." However, to maintain proper drive characteristics, it is important to avoid premature exit of the exit tooth 70 from the exit sheave 72. The drive mechanism resulting from the pitch difference is described in more detail in U.S. Patent Application No. 60/593,493, which is incorporated herein by reference in its entirety.

Referring back to Fig. 1, the conveyor 10 according to one aspect of the invention comprises a pair guide assemblies, an upper span guide assembly 80 and a pulley guide assembly 82. The upper span guide assembly 80 is located at the juncture between the straight section 12 and the inclined section 14 (hereinafter referred to as "the juncture") at the upper span 28, and the pulley guide assembly 82 is located at the drive pulley 18. The upper span guide assembly 80 and the drive pulley guide assembly 82 prevent buckling of the belt 16 at the juncture and at the drive pulley 18, respectively. The pulley guide assembly 82 also prevents premature exiting of the exit tooth 70 from the exit sheave 72, as will be described in detail below.

As shown in the lateral sectional view of Fig. 4, the upper span guide assembly 80 comprises a pair of lateral guides 90 positioned below the lower, toothed surface 34 of the belt 16. Each of the lateral guides 90 is located along one of the side edges 36, 38 of the belt 16 and can be mounted to a frame of the conveyor 10 or any other support, which is shown generically by the reference numeral 92 in the figures. The lateral guide 90 extends laterally inward from the respective support 92 and comprises an upwardly extending projection 94 sized for receipt within one of the gaps 44 in the belt teeth 40, and having a surface 95 facing outwardly in a position to abut the faces 43 of the edge tooth portions 42B. Consequently, as the faces 95 and 43 abut, the projection 94 counteracts the tendency of the corresponding side edge 36, 38 of the belt 16 to move laterally inwardly by exerting a force in the direction of arrow 96 away from a longitudinal center of the belt 16. In other words, it prevents migration of the corresponding side edge 36, 38 toward the longitudinal center. Because the lateral guides 90 are positioned on opposite side edges 36, 38, the lateral guides 90 prevent the belt 16 from buckling. Preferably, the gaps 44 (and thereby the teeth 40) and the guide projections 94 have about the same thickness, or, alternatively, the projections 94 can have a thickness greater than the thickness of the gaps 44 (and thereby the teeth 40). As used herein, the thickness of the projection 94 refers to the vertical thickness or the distance that the projection 94 projects upward from the rest of the lateral guide 90. As a result of the thickness of the projection 94 relative to the thickness of the gap 44, the lower surface 34 of the belt 16 rests on the projections 94, even at the sections of the projections 94 between adjacent teeth 40, as illustrated in the longitudinal sectional view of Fig. 5. As also shown in Fig. 5, the lateral guides 90 are contoured according to the contour of the

belt 16 at the juncture. Additionally, the lateral guides 90 can extend along any desired length of the belt 16 at the juncture and can be positioned at one location or several locations along the juncture.

With continued reference to Figs. 4 and 5, the upper span guide assembly 80 further comprises a pair of guide shoes 100 positioned above the upper, load-bearing surface 32 of the belt 16. Like the lateral guides 90, each of the guide shoes 100 is located along one of the side edges 36, 38 of the belt 16 and can be mounted to the frame of the conveyor 10 or any other support 92. The guide shoe 100 extends laterally inward from the respective support 92 and is positioned relative to the belt 16 to help maintain engagement of the belt 16 with the lateral guide 90 (i.e., engagement of the gap 44 with the projection 94) and prevent the belt 16 from moving upward and slipping over the projection 94. The guide shoe 100 can physically contact the belt upper surface 32 or can be spaced from the upper surface 32 to reduce drag on the belt 16. While the guide shoe 100 can have any suitable lateral width, the guide shoe 100 in the illustrated embodiment is sufficiently wide so that the guide shoe 100 is positioned above the corresponding projection 94, as shown in Fig. 4. As shown in Fig. 5, the guide shoes 100, like the lateral guides 90, are contoured according to the contour of the belt 16 at the juncture. In the illustrated embodiment, the guide shoe 100 has a guide surface 102 facing the belt 16 and contoured according to the contour of the belt 16. The guide shoe 100 can have any suitable shape or form and is not intended to be limited to that shown in the figures. Additionally, the guide shoes 100 can extend along any desired length of the belt 16 at the juncture and can be positioned at one location or several locations along the juncture.

Referring now to the lateral sectional view of Fig. 6, the pulley guide assembly 82 is similar to the upper span guide assembly 80 in that it comprises a pair of lateral guides 110 and a pair of guide shoes 120. The lateral guides 110 are essentially identical to the lateral guides 90 of the upper span guide assembly 80 and are positioned above the lower, toothed surface 34 of the belt 16 adjacent to outermost individual pulleys 112 of the drive pulley 18. Each of the lateral guides 110 is located along one of the side edges 36, 38 of the belt 16 and can be mounted to a frame of the conveyor 10 or any other support, which is shown generically by the reference

numeral 114 in the figures. The lateral guide 110 extends laterally inward from the respective support 114 and comprises a downwardly extending projection 116 sized for receipt within one of the gaps 44 in the belt teeth 40 and having a surface 117 facing outwardly in a position to abut the faces 43 of the edge tooth portions 42B. The projections 116 function like the projections 94 to prevent buckling of the belt 16.

The guide shoes 120 are similar to the guide shoes 100 of the upper span guide assembly 80 and are positioned below the upper, load-bearing surface 32 of the belt 16. Each of the guide shoes 120 is located along one of the side edges 36, 38 of the belt 16 and can be mounted to the frame of the conveyor 10 or other support 114. The guide shoe 120 helps maintain engagement of the belt 16 with the corresponding lateral guide 110 (i.e., engagement of the gap 44 with the projection 116) and prevents the belt 16 from moving downward and away from the corresponding lateral guide 110. Referring back to Fig. 2, a guide surface 102 of the guide shoe 120 faces the belt 16 and is contoured according to the contour of the belt 16 as it wraps around the drive pulley 18. Due to the location of the guide shoes 120 relative to the belt 16 and the drive pulley 18, the guide shoes 120 function to maintain engagement between the exit tooth 70 on the belt 16 and the exit sheave 72 on the drive pulley 18 and thereby prevent premature exiting of the exit tooth 70 from the exit sheave 72. The guide shoes 120 can be located in any suitable location to prevent premature exiting of the guide tooth 70, and exemplary locations are described with respect to a position limiter in the aforementioned and incorporated patent application. While the guide shoe 120 can have any suitable longitudinal width, the guide shoe 120 in the illustrated embodiment has a longitudinal width about equal to the spacing between the belt teeth 40, i.e., the belt pitch Pbeit. It has been determined that such a longitudinal width is especially effective at preventing premature exiting of the exit tooth 70 from the exit sheave 72. Optionally, the guide shoes 120 can be in the form of a single guide shoe that extends across the entire lateral width of the belt 16, such as when the belt 16 does not have any features, such as the cleats, on the upper surface 32.

The lateral guides 90, 110 and the guide shoes 100, 120 can be made of any suitable material. To minimize drag between the belt 16 and the lateral guides 90, 110 or the guide shoes

100, 120, in the event that the belt 16 contacts the lateral guides 90, 110 or the guide shoes 100, 120, the lateral guides 90, 110 and the guide shoes 100, 120 can be made of or coated with a material having a relatively low coefficient of friction. For example, the lateral guides 90, 110 and the guide shoes 100, 120 can be coated with a friction reducing material, such as polytetrafluoroethylene (PTFE), also known as Teflon ^® . Additionally, the lateral guides 90, 110 and the guide shoes 100, 120 can be designed to have a minimum surface area that contacts the belt 12.

During operation of the conveyor 10, the drive pulley 18 rotates about the shaft 22, and the drive pulley sheaves 62 engage the belt teeth 40 to transmit torque to the belt 16 as described above. As the upper span 28 moves from the straight section 12 to the inclined section 14, the belt 16 passes though the upper span guide assembly 80, which acts to prevent buckling of the belt 16 and facilitates bending of the belt 16 at the juncture between the straight section 12 and the inclined section 14. In particular, the projections 94 on the lateral guides 90 effectively pull the belt 16 laterally or otherwise prevent inward movement of the belt 16 to prevent belt buckling, and the guide shoes 100 help maintain engagement between the projections 94 and the gaps 44 in the belt teeth 40. As the belt 16 wraps around the drive pulley 18, the belt 16 passes through the pulley guide assembly 82; this acts to prevent buckling of the belt 16 and prevents premature exiting of the exit tooth 70 from the exit sheave 72. In particular, the projections 116 on the lateral guides 110 effectively pull the belt 16 laterally or otherwise prevent inward movement of the belt 16 to prevent belt buckling, and the guide shoes 120 prevent the belt 16 from moving downward relative to the lateral guides 110 and hold the exit tooth 70 in the exit sheave 72 to ensure proper drive characteristics.

The conveyor 10 has been shown in the figures and described above in a configuration with the drive pulley 18 and the single idler pulley 20; however, it is within the scope of the invention for the conveyor 10 to have other configurations, such as a center drive conveyor with a pair of idler pulleys and a drive pulley.

The guide assemblies 80, 82 can be employed with any conveyor having a toothed endless thermoplastic belt and is not limited to use with conveyors having the drive

characteristics described above and in the aforementioned and incorporated patent application. The guide assemblies 80, 82 can also be positioned at different locations on the conveyor 10 and can be utilized with other configurations of conveyors, including conveyors with only straight sections. An exemplary straight conveyor 210 with guide assemblies according to another embodiment of the invention is illustrated in Fig. 7. The conveyor 210 is similar to the conveyor 10 of Fig. 1, except that the conveyor 210 comprises only the straight section 212, the belt 216 includes a plurality of longitudinally spaced cleats 233 on the load-bearing or upper surface 232, and the guide assemblies are present in the form of a return span guide assembly 280 and a drive pulley guide assembly 282. The return span guide assembly 280 is substantially identical to the upper span guide assembly 80, including a guide 90, but is flipped upside down to accommodate the orientation of the belt 216 at the return span 230. The return span guide assembly 280 not only prevents buckling of the belt 216, such as in the areas between the cleats 233, but also prevents the belt 216 from sagging on the return span 230. The drive pulley guide assembly 282 is identical to the drive pulley guide assembly 82 for the swan neck conveyor 10, including the guide 110. The drive pulley guide assembly 282 is especially useful for the conveyor 210 in Fig. 7 when the cleats 233 are relatively wide (e.g., thirty-five inch wide cleats on a thirty-six inch wide belt). In such a conveyor, the position limiter described in the aforementioned and incorporated patent application cannot be utilized because there is not sufficient space for the position limiter at the edges 236, 238 of the belt 216 due to the wide cleats 233. However, the drive pulley guide assembly 282 can be employed rather than the position limiter because the drive pulley guide assembly 282 does not require the amount of space that the position limiter requires. Further, because the drive pulley guide assembly 282 keeps the belt 216 from buckling at the drive pulley 218, the belt 216 maintains engagement with each of the individual pulleys of the drive pulley 218.

While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.