Split sprocket assembly

Abstract: A split power transmission element, such as a sprocket (10), mountable on a driven shaft. A pair of substantially identical sprocket halves (14,16) each include a pair of aligned, hollow, fastener sleeves (38,40) extending diagonally through the plane of the sprocket. A pair of fasteners (44) within the sleeves (38,40) join the sprocket halves (14,16) to each other and clamp the sprocket (10) onto the shaft. The diagonal orientation of the fastener (44) sleeves permits convenient disassembly of the sprocket from an upwardly located, axially displaced position. The sprocket halves (14,16) are substantially identical and can be economically molded using a single mold. A keyway insert (36) distributes driving forces throughout the sprocket hub and increases the maximum torque capacity of the sprocket (10).

Description: The present invention relates to power transmission elements. Power transmission element, such as gears, pulleys, sheaves and sprockets of various types are used in a variety of applications. In one common application found, for example, in conveyor systems used in the beverage industry, one or more sprockets are mounted on an elongate drive shaft. As the shaft rotates, the sprockets turn to advance the conveyor. For any number of reasons, it may be necessary to remove or replace a sprocket or other such power transmission element. When conventional one-piece sprockets are used, it is necessary to expose at least one end of the shaft so that the sprockets can be removed over the exposed end. This is a complicated and cumbersome procedure that can take considerable time and require shutting down conveying operations for an extended period. Valuable production time can thus be lost. To simplify the repair and replacement of such sprockets, there have been proposed various types of split sprockets. These sprockets, formed in two or more sections, can be mounted on, and removed from, a driven shaft while the shaft remains in place. Use of such split sprockets greatly simplifies the removal and replacement of the sprocket and reduces the machine "downtime" required to implement maintenance and repair. Such sprockets can be formed of various materials, such as thermoplastic as well as metals. Various means have been developed for fastening the split sprocket mating sections together and the sprocket to the driven shaft. Such split sprockets are known from e.g. FR-A-407483 and FR-A-2424452. In the aforementioned FR-A-2424452 there is generally disclosed a power transmission element mountable on a shaft, comprising a pair of power transmission element components, each of said power transmission element components having a generally semi-circular configuration and integrally including a hub portion configured to directly overlie a portion of the shaft and further including a pair of substantially parallel fastener means on opposite sides of the shaft axis, and further comprising a fastener within each of said fastener means for joining said power transmission element components to each other to form the power transmission element having a central hub shaped and dimensioned to encircle the shaft. However, this generally disclosed power transmission element has the disadvantage that, although effective in clamping the sprocket to the shaft, because the fastener means are oriented perpendicular to the axis of the shaft, this arrangement is somewhat complex and difficult to service as at least some of the fasteners are in difficult to reach locations. In accordance with the invention as claimed, the aforesaid generally disclosed power transmission element is characterized in that said fastener means are oriented diagonally relative to the plane of rotation of the power transmission element component. An advantage of the present invention is that the diagonally disposed fastener sleeves are positioned to optimize clamping forces while allowing easy access for service and repair. In an advantageous development of the invention, each of the power transmission element halves also includes at least one set of alignment teeth matingly disposed on the power transmission element cross sectional surfaces which join the two power transmission element halves together. The alignment teeth also interlock and are angularly disposed to resist sheering forces tending to separate the sprocket halves. These alignment teeth can also be oriented to reinforce the vector clamping force applied via the fastener sleeves. In order that the invention may be well understood, there will now be described some embodiments thereof, given by way of example, reference being made to the accompanying drawings, in which: FIGURE 1 is a perspective view of one embodiment of a split sprocket constructed in accordance with the invention. FIGURE 2 is a side elevation view of the split sprocket shown in FIG. 1. FIGURE 3 is a perspective view of another embodiment of a split sprocket constructed in accordance with the invention. FIGURE 4 is a side elevation view of the split sprocket shown in FIG. 3. FIGURE 5 is a cross-sectional view of the split sprocket shown in FIG. 3 taken along line 5-5 thereof. FIGURE 6 is a cross-sectional view of the split sprocket shown in FIG. 3 taken along line 6-6 thereof. FIGURE 7 is a cross-sectional view of the split sprocket shown in FIG. 3 taken along line 7-7 thereof. FIGURE 8 is a force diagram illustrating the various forces developed in an assembled split sprocket constructed in accordance with the invention. FIGURE 9 is a sectional view of one embodiment of a split sprocket constructed in accordance with one aspect of the invention illustrating the use of a metallic keyway insert. FIGURE 10 is a perspective view of the metallic keyway insert shown in FIG. 9. FIGURE 11 is a front elevation view of another embodiment of a split sprocket constructed in accordance with the invention showing the use of a plurality of gripping pads in the hub area thereof. Referring first to FIGS. 1 and 2, a split power transmission element comprises a split sprocket 10. It will be appreciated, however, that the invention is equally applicable to other forms of power transmission elements such as gears, pulleys and sheaves. As illustrated, the split sprocket 10 comprises a generally disk-shaped member having a central hub 12 shaped and dimensioned to encircle a driven shaft such as keyed (FIG. 9) or unkeyed drive shaft (not shown). The sprocket 10 comprises a pair of substantially identical sprocket halves 14 and 16, each half having a generally semi-circular configuration. Each of the sprocket halves 14 and 16 includes a generally diametrically extending lower edge 18, a pair of opposed faces 20 and 22, and a circumferential outer edge 24 having thereon formed a plurality of sprocket teeth 26. A hub portion 28 is also formed in each of the halves 14 and 16 and is shaped to overlie a portion of the drive shaft. Each of the hub portions 28 includes a hollow interior 30 that defines a central axis 32 that is oriented coaxially with the longitudinal axis of the shaft when the hub portion 28 overlies the shaft. In the illustrated embodiment, the sprocket 10 is configured for mounting on a keyed drive shaft 34 (FIG. 9). Accordingly, one of the sprocket halves 14 includes a keyway 36 for receiving therein a drive shaft key. The other sprocket half 16, which otherwise can be identical with the first sprocket half 14, does not include the keyway 36. Preferably, both sprocket halves 14 and 16 are moulded of a thermoplastic material. FIGS. 3 and 4 illustrate another embodiment of the split sprocket 10 wherein it is intended that the split sprocket 10 be mounted on an unkeyed shaft. In this embodiment, neither of the sprocket halves 14 or 16 includes the keyway 36. The sprocket halves 14 and 16 are identical, and the same mould can be used for forming each half. In use, the sprocket halves 14 and 16 are placed around the drive shaft 34 and are fastened to each other to thereby lock the sprocket 10 to the shaft 34. To this end, and as shown in FIGS. 3 and 4, each sprocket half 14 and 16 includes a pair of fastener sleeves 38 and 40 located on opposite sides of the hub portions 28. The sleeves 38 and 40 extend diagonally through the disk or body portions 20, 22 of each of the sprocket halves 14 and 16. As illustrated, the sleeves 38 and 40 are hollow and are oriented so that when the diametric edges 18 and the surfaces 19 and 21 and the surfaces 19 and 21 of the sprocket halves 14 and 16 are brought together, hollow interiors 42 of the opposed sleeves 38 and 40 on opposite sides of the diametric edges 18 are substantially coaxially aligned with each other. A pair of fasteners 44, one in each pair of aligned sleeves, fasten the sprocket halves 14 and 16 to each other. Preferably, each of the fasteners 44 comprises a metallic nut 46 and bolt 48. The nut 46 preferably comprises a threaded insert, having a fluted outer surface 50 and an enlarged or flanged end 52. Preferably, each nut 46 is press fitted within the fastener sleeve 38 or 40 as shown in FIG. 5. As illustrated in FIG. 5, each of the fastener sleeves 38 and 40 is oriented so that its hollow interior 42 lies substantially within a plane oriented parallel relative to the central axis 32 of the hub portions 28 and perpendicularly relative to the diametric edge 18. In addition, each of the fastener sleeves 38 and 40 is oriented so that central axis of its hollow interior 42 passes substantially through the midline of the diametric edge 18. When so oriented, the forces F 1 and F 2 developed by each fastener 44 include a shear component directed axially relative to the drive shaft and a clamping force directed radially relative to the drive shaft. These vector forces are illustrated in FIG. 8. The clamping forces thus developed by each of the fasteners 44 serve to clamp the sprocket 10 firmly onto the drive shaft 34. As further illustrated in FIG. 8, the vector forces exerted by the fasteners 44 also develop shear force components that tend to displace the sprocket halves 14 and 16 laterally relative to each other. To overcome this shearing tendency, means are provided for preventing axial movement of the sprocket halves 14 and 16 relative to each other as the fasteners 44 are tightened. In the illustrated embodiment, such preventing means comprise a plurality of interlocking alignment teeth 54 and sockets 56 formed in the diametric edges 18 of the sprocket halves adjacent the hub portions 28 thereof. As best seen in FIGS. 6 and 7, the sides of the interlocking teeth 54 are preferably oriented at an angle of approximately 15° relative to the plane of the sprocket 10 to best resist the shearing forces developed by the fasteners 44. Preferably, the fastener sleeves 38 and 40 are oriented at substantially a 30° angle relative to the plane of the sprocket 10. These angular relationships provide good clamping forces and resistance to these forces generally while still permitting east access to the fasteners 44 for service and repair of the sprocket 10. Further details of the latter feature will be described hereinafter. In addition to developing a substantial clamping force for securing the sprocket 10 to the drive shaft 34, another advantage of the diagonally oriented fastener sleeves 38 and 40 is that access to the head of each of the fasteners 44 can be obtained from a position above and to the side of the sprocket 10 itself. This eliminates the need to approach the sprocket 10 from underneath, and the lateral offset permits the sprocket 10 to be disassembled without interference from an overlying structure such as a conveyor belt (not shown). To maximize the torque capacity of the sprocket 10 when the sprocket 10 is mounted on the keyed shaft 34, one of the sprocket halves 14 is preferably provided with a metallic keyway insert 58 that engages a key 60 and helps distribute the resulting driving forces to the hub 12 while avoiding deformation of the thermoplastic material forming the sprocket 10. Another embodiment of the invention is illustrated in FIG. 11. In this embodiment, the sprocket 10 is intended for mounting on an unkeyed shaft (not shown). To improve the torque transfer characteristics between the shaft and the sprocket 10, a plurality of intergrally molded gripping pads 62 are formed along the axial bore 30 of the hub 12. These pads 62 deform under the clamping forces developed as the fasteners 44 are tightened and thus serve to grip the shaft and thereby improve the torque transfer characteristic between the shaft and the sprocket 10. Although various embodiments of the invention have been described, it will be appreciated that various modifications can be made. For example, various fastener types other than the nuts and bolts shown and described can be employed within the fastener sleeves. Furthermore, the thermoplastic material making up the sprocket halves is not critical. Additionally, the configuration and orientation of the sprocket teeth around the sprocket circumference are also not critical. Finally, as previously noted, the invention is equally well suited for use with other forms of power transmission elements, such as gears, pulleys and sheaves.

Claims: A power transmission element mountable on a shaft (34), comprising a pair of power transmission element components (14, 16), each of said power transmission element components (14, 16) having a generally semi-circular configuration and integrally including a hub portion (28) configured to directly overlie a portion of the shaft (34) and further including a pair of substantially parallel fastener means (38, 40) on opposite sides of the shaft axis (34), and further comprising a fastener (44) within each of said fastener means (38, 40) for joining said power transmission element components (14, 16) to each other to form the power transmission element (10) having a central hub (12) shaped and dimensioned to encircle the shaft (34), characterized in that said fastener means (38, 40) are oriented diagonally relative to the plane of rotation of the power transmission element component (14, 16). A power transmission element as claimed in claim 1, further comprising means (54, 56) for preventing axial movement of said power transmission element components (14, 16) relative to each other as said fasteners (44) are tightened. A power transmission element as claimed in claim 2, wherein said preventing means (54, 56) includes protrusions (54) arranged to interlock with each other when said power transmission element components (14, 16) are joined to each other. A power transmission element as claimed in any of the preceding claims, wherein each of said fastener means (44) includes a sleeve (38, 40) having a hollow interior (42) and wherein the hollow interiors (42) of adjacent sleeves (38, 40) on the same side of said hub portion (28) are substantially coaxially aligned when said power transmission element components (14, 16) are oriented for joining to each other. A power transmission element as claimed in claim 4, wherein said power transmission element (10) includes two fasteners (44), each of said fasteners (44) extending through the coaxially aligned hollow interiors (42) of an adjacent pair of said sleeves (38, 40). A power transmission element as claimed in claim 1, wherein each of said generally semi-circular power transmission element components (14, 16) comprises an outer circumference (24), a diametric edge (18) and a face (20; 22), said hub portion (28) of each component (14, 16) being formed along the diametric edge (18) and defining a central axis (32) oriented coaxially with the longitudinal axis of the shaft (34) when said hub portion (28) overlies the drive shaft (34), said pair of substantially parallel fastener means (38, 40) comprising a first fastener sleeve (38) on one side of said hub portion (28) having a hollow interior (42), said hollow interior (42) extending diagonally through said face (20; 22) substantially in a plane oriented substantially perpendicularly to said central axis (32) and substantially perpendicular to said diametric edge (18), and a second fastener sleeve (40) on the opposite side of said hub portion (28) having a hollow interior (42) oriented substantially parallel to the hollow interior (42) of said first fastener sleeve (38). A power transmission element half as claimed in claim 6, further comprising means (54, 56) for preventing axial movement of said power transmission element half (14) relative to a similar power transmission element half (16) when said power transmission element half (14) is mated to the similar power transmission element half (16) along said diametric edge (18). A power transmission element half as claimed in claim 7, wherein said preventing means (54, 56) comprises a plurality of protrusions (54) formed along said diametric lower edge (18), said protrusions (54) being located and shaped so as to interlock with similar protrusions (54) formed along the diametric edge (18) of the similar power transmission element half (16). A power transmission element as claimed in any of the preceding claims, wherein said power transmission element is a conveyor sprocket and each of said power transmission element components (14, 16) is a sprocket element.

Inventors: GLADCZAK ROBERT J, GRUETTNER DAVID R, MENTZER EDWARD W, GLADCZAK, ROBERT J, GRUETTNER, DAVID R, MENTZER, EDWARD W
Applicants: UCC CORP, UCC CORPORATION
Application year: 1991
Main classification: F16H55
IPC codes: F16D1, F16H55