Endless belt power transmission systems or components – Hub formed in sections and separable by moving sections...
Reexamination Certificate
2002-01-31
2004-07-06
Hannon, Thomas R. (Department: 3682)
Endless belt power transmission systems or components
Hub formed in sections and separable by moving sections...
C198S834000
Reexamination Certificate
active
06758776
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the conveyor art and, more particularly, to an improved split sprocket assembly, a related apparatus, and a related method of mounting a sprocket to a rotatable structure, such as a drum or shaft.
BACKGROUND OF THE INVENTION
Today, in many modern manufacturing facilities, modular conveyor systems are extensively utilized to transport articles to and from various work stations during all stages of production. In recent years, manufacturers using production lines with conveyors as an integral component of the material handling system have realized reasonably significant gains in productivity and resource utilization. As a result, modular conveyor systems have become even more widely implemented and have been adapted to meet an even wider scope of the material handling needs of producers of a multitude of consumer and industrial goods. Therefore, the continual development of improved modular conveyors is necessary in order to keep pace with the demands and expectations of the users of such conveyors.
Conventional conveyor systems employing endless, modular link or roller chain belts are typically driven at one end of an elongated guide structure, such as a rail or the like supported above the ground by a frame. The driving force is transmitted from a motive device, such as a variable speed electric motor, to a plurality of gang-driven sprockets coupled to a rotating drive structure, such as a shaft or drum. At the opposite end of the guide structure, idler sprockets are coupled to a freely-rotating idler shaft or drum. As should be appreciated, the drive and idler sprockets assist in supporting and guiding the endless belt as it makes the transition from the forward run to the return run, or vice versa, at each respective end of the guide structure.
Of course, both the drive and idler sprockets are subject to wear as a result of the substantially continuous engagement maintained with the conveyor belt. If not kept in check, this wear may affect the overall performance of the conveyor system. For example, worn sprockets may allow the belt to slip, which creates both timing and efficiency problems. Hence, it is necessary to perform an inspection of the sprocket(s) from time to time to determine whether some form of ameliorative action, such as a repair operation or perhaps even a complete replacement, is required.
While inspection may only require removing the belt to gain visual access to the sprocket, repairing or completely replacing a unitary sprocket requires removing it from the corresponding support shaft or drum altogether. In the case where a single drive or idler sprocket is carried on the shaft or drum, removing the belt and the sprocket is a relatively uncomplicated undertaking. However, in the situation where a plurality of sprockets are gang driven or carried on a single support shaft or drum, removing any of the inner sprockets becomes a time and labor intensive process, since all adjacent outer sprockets and any other corresponding structures (side plates, chain guides/strippers, conveyor frame components or other support structures, etc.) must first be removed. As should be appreciated, removing even one of the sprockets in a gang-driven arrangement significantly increases the time and labor involved. Additionally, the wholesale removal and replacement of multiple sprockets carried on a shaft may create alignment and/or timing problems that must be corrected to ensure efficient operation. Of course, the time and labor required to remedy these problems further exacerbates the situation.
Others in the past have proposed a number of different types of arrangements to solve these problems. One popular proposal is to use a split sprocket consisting of two mating halves that are coupled together over a shaft. With this arrangement, removal of the sprocket can be accomplished without dismantling the entire conveyor assembly. Modem examples of various types of split sprockets are found in U.S. Pat. No. 6,202,834 to Layne et al, U.S. Pat. No. 6,146,299 to Harvey, and U.S. Pat. No. 6,086,495 to Stebnicki et al., the disclosures of which are hereby incorporated by reference.
In the case of a rotatable drive or idler drum, it is known to couple a single-piece, unitary sprocket to the drum using a plurality of cylindrical keys or pins. For example, U.S. Pat. No. 5,934,447 to Kanaris discloses an arrangement in which the drum includes a plurality of shallow grooves extending axially along its entire surface. Keys received in the sprocket fit in the corresponding shallow grooves and, as a result, keep it spaced from the outer surface of the drum. A radially extending set screw is used to press each key into the corresponding groove to rotatably couple the sprocket to the drum.
While this arrangement does provide the limited advantage of allowing for the adjustment of the position of the sprocket along the drum, there are countervailing disadvantages. For example, during extended periods of use, the set-screws may loosen and allow the keys and, hence, the sprocket to “walk” or travel axially along the surface of the drum. This is deleterious, since it not only increases the wear on the sprocket, but also causes chattering and wear on the belt. If the set-screws loosen to a sufficient degree to allow the key to move out of the shallow groove in the drum, the sprocket may slip and, in the case of a driven drum, transmit no drive power or torque to the belt. Of course, the set-screws may be frequently inspected or tightened down in an effort to prevent these deleterious occurrences, but this inevitably increases the maintenance effort and overall operational cost.
Accordingly, the foregoing discussion identifies a particular need for an improved manner of mounting a sprocket to a rotatable structure, such as a drive or idler drum in a conveyor system. It is envisioned that by splitting the sprocket into two or more sections or segments, it would be possible to provide a key for each section or segment that corresponds to a separate keyway formed in the outer surface of the rotatable structure. The sections or segments could also be coupled together and held in tension, such as by tangentially-extending fasteners. The tension would create a sufficient radially-directed holding force to ensure that the keys remain securely held in the keyways during rotation while eliminating the need for radially-extending set-screws. One or more of the keyways could also be truncated and the keys sized for fitting in the truncated keyway(s) in relatively tight seated engagement. This would prevent the sprocket from traveling or “walking” along the surface of the drum in use. Overall, this combination of features would result in a sprocket assembly that is a significant improvement over those proposed in the past, especially in terms of maintenance cost, operational efficiency, and reliability.
SUMMARY OF THE INVENTION
In accordance with a first aspect of the invention, a sprocket assembly intended for mounting on a rotatable structure, such as a drum or shaft, for engaging an endless conveyor belt making the transition between a forward and a return run or vice-versa is disclosed. The assembly comprises at least three unitary sprocket sections or segments, with each of the sections or segments including an arcuate inner surface for engaging an outer surface of the rotatable structure. A plurality of fasteners are also provided, each for fastening one of the plurality of sprocket sections to an adjacent sprocket section to form the sprocket assembly.
Each of the arcuate sprocket sections or segments includes a first end and a second end. In one embodiment, the first end includes a tangentially-extending bore and the second end includes a corresponding aperture for receiving a threaded bolt forming a part of one of the fasteners. The engagement of the bolt extending through the aperture in the first end of one sprocket section or segment into the bore in a second end of the adjacent sprocket section or segment assists in securing the two structures toge
Fye Stephen C.
Layne James L.
McDaniel Michael D.
Hannon Thomas R.
King & Schickli PLLC
Span Tech LLC
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