Overhead Trolley Conveyor

Overview

An overhead trolley conveyor is the simplest form of overhead conveyor: a single endless chain runs around a fixed loop of track hung from the roof, and every carrier attached to that chain moves together at one steady speed. There is no accumulation and no routing, so it is the right choice when a process is continuous and every part takes the same path, such as a paint line, a plating line, or an oven where parts hang from the chain and move through the work at a fixed rate. By lifting the load off the floor it frees the floor for people and other equipment, and by hanging parts it presents every side of them to spray, dip, or weld.

The conveyor is built from a Overhead Track loop, a single Conveyor Chain that runs it, the Trolleys and Carriers that ride the track and carry the load, a Drive Unit that pulls the chain, a Take-Up Unit that keeps it taut, the Turns and Vertical Curves that route it around the plant, and a Control and Safety for safe operation.

The track loop

The Overhead Track is a continuous rail that the trolley wheels run on, usually an I-beam or a formed-steel section. It is made up of straight Track Section lengths joined by bolted Track Joint splices, and the whole loop hangs from the building on Hanger Rod rods through Support Bracket brackets. The track layout is the route the parts will travel, so it is designed to weave the loop through the spray booths, ovens, and load and unload stations, climbing and dropping as needed. Because all carriers share the loop, the track length and the chain speed together set how long a part spends in each zone.

Chain and trolleys

A single Conveyor Chain carries the whole load. It is built from forged Chain Link links joined by hardened Chain Pin pins, with Pendant Attachment links at regular spacing that hang the carriers. Each carrier rides on a Trolley, a pair of Trolley Wheel wheels on Ball Bearing bearings held in a Trolley Yoke yoke and turning on an Trolley Axle. Below the trolley a Pendant drops to a Load Carrier that holds the part, and a Swivel Joint joint lets the carrier rotate so parts keep their orientation through corners. Carriers are matched to the job, from simple hooks for painting to baskets for plating to shaped fixtures for assembly.

Drive and take-up

The Drive Unit pulls the chain at one constant speed. A Drive Gearmotor feeds a Drive Shaft carrying a Drive Sprocket that meshes the chain, and a Shear Pin breaks on overload to protect the gearbox if a carrier snags. Because the chain stretches as the pins wear and the line heats up, a Take-Up Unit unit keeps it taut. A spring-loaded Take-Up Carriage slides a Take-Up Sprocket to add or remove chain length, which stops the chain jumping the drive sprocket and keeps wheel spacing even. On long ovens an air take-up is used instead of springs so tension stays steady as the chain expands with heat.

Turns and elevation changes

Routing the loop through a plant needs corners and rises, which the Turns and Vertical Curves section provides. A horizontal corner is taken on a large Turn Wheel or a Roller Turn bank of small rollers that guides the chain around with low friction. To move between floor levels or to lift parts over equipment the loop uses Vertical Curve Section sections, which are curved track that the trolleys follow up and down. The radius of every turn is set by the chain and the load so the chain articulates freely and the carriers do not swing into each other.

Control and safety

The Control and Safety is simpler than on a power-and-free system because there is nothing to route. A Variable-Frequency Drive sets the chain speed and ramps it smoothly, and a Control Board runs the line logic and watches the safety devices. Jam Switch switches along the track stop the drive if a carrier snags or the chain breaks, and a Pull-Cord E-Stop pull-cord lets anyone stop the loop from any point. The electronics share a Power Supply and report to an LCD Panel screen.

Use and variants

Overhead trolley conveyors are chosen where a steady, single-speed pass is what the process needs. In a paint or powder-coat line the loop carries parts through cleaning, spraying, and a curing oven at a rate that matches the cure time. In plating and anodizing it dips parts through tanks in sequence. In assembly it presents parts at a fixed pace to a row of workers. The main variants are by track type, light formed-rail systems for small parts and heavy I-beam systems for large weldments, and by environment, with high-temperature chain and lubricant for oven duty and corrosion-resistant finishes for plating areas. What stays constant is the principle: one chain, one loop, one speed, with every carrier moving in lockstep.