Overhead trolleys are conveyors that consist of a continuous loop of chain or cable that is suspended from a track. Carriers are attached periodically to hang or contain products. There are several different types of overhead trolleys. Manual trolleys or push systems are used mainly in low-volume applications. Motorized overhead trolleys have wheels that run on a rail and are driven by a motor. The trolley wheels are sealed and feature a full-ball complement, retainer-type design, or journal bearing construction. Power-and-free (P&F) conveyors consist of a continuously-moving powered chain that, when engaged, moves a free (non-powered) load-carrying trolley through the material handling system. Overhead trolleys are one of two types of P&F conveyors. The other type is the inverted trolley.
Overhead trolleys are used in automated and semi-automated painting systems to move parts through cleaning and coating operations. They are also used in other industrial applications. Examples include transporting products between manufacturing operations, providing a continuous supply of empty cartons, and carrying parts or products overhead during drying or cooling activities. Some overhead trolleys are used to move loads up to several thousand pounds. Other overhead trolley systems are designed for high load, high temperature, and high contamination applications. Overhead trolleys provide two significant advantages over other types of industrial conveyors. First, because they are overhead and out of the way, these material handing systems use space efficiently. Second, overhead trolleys can handle odd-shaped parts that are difficult to convey on belt or roller-style conveyors.
Selecting overhead trolleys requires an analysis of product specifications and available options. The type of cable or chain is an important consideration. In a power-and-free system, the chain is located in the upper, powered portion of the overhead trolley and fitted with dogs that engage and push the carrier. The lower portion of the conveyor system has a wheeled trolley that carries the load and runs on channels, structural angles, or a trolley track. There is no positive bolted, fixed, or pinned connection between the power pusher and the free trolley; however, vertical and horizontal changes in the trolley path can be negotiated. Available options for overhead trolleys include collectors, dead ends, hangers, feeds, splice kits, and stripping tools.