This invention relates to chain assemblies and pivot pins therefore and, more particularly, to a pivot pin assembly for chains and especially conveyor chains.
Conveyor chains, and especially those used in overhead conveyors typically include a center link with side links pivotally connected to each end of the center link by pivot pins. The center link is secured to a trolley bracket supported by trolley wheels on a rail. A sprocket or drive gear imparts movement to the chain for conveying suspended items along the rail.
One common prior known type of pivot pin used in such chain includes an integral, enlarged head at each end which retains the side and center links together along the pin. Such pins are inserted through enlarged apertures in the links and slid into their final position. In order to prevent disassembly of such "rivetless" chains, locking, non-rotational pins are used, i.e., pins with pin heads which are typically elongated and parallel to one another. The end of each center link is wider than its center portion. The pins are inserted through the three links, and rotated such that the elongated heads are received in recesses on the exterior sides of the side links. Extension or tightening of the chain causes the wider end of the center link to force the side links apart preventing the elongated heads from rotating out of their side link recesses.
Rivetless chain is expensive to manufacture because of required forging or machining of the pins and links, and the required tools and dies therefore. Also the elongated heads of the above-described pins prevent rotation, causing continuous wear of only one portion of the pin and reduced life or more frequent repair of the chain.
Certain chains with rotatable, wear compensating pins have also been proposed. Such pins typically include a cotter pin or other removable fastener retaining a washer at one end of the pin to hold the links in position. However, because of the constant motion, vibration and stress imposed on the conveyor chain as well as other industrial operations which occur in the environment in which conveyor chains are used, it has been found that such removable fasteners are often lost, broken or knocked loose resulting in chain disassembly, high maintenance costs, and frequent down time for conveyor lines.
The present invention was conceived as a solution to the above problems of wear, chain disassembly and pivot pin manufacture.