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What Is a Ball Transfer Unit?

Paul Scott
Paul Scott

A ball transfer unit is an omni-directional, low-friction material transport device that makes up part of specialized conveyor systems. The ball transfer unit consist of a large, precision ball bearing locked in a metal enclosure with its upper area protruding. The lower edge of the ball bearing rests on a layer of smaller ball bearings, also locked in place in the enclosure. This allows the large ball to rotate freely in all directions with very little friction. Rows of ball transfer units are mounted in lines on metal runners, which are, in turn, mounted side-by-side on the conveyor bed offering a large area of free rotating balls over which material can be passed smoothly in any direction.

Conveyor systems are a widely-used standard in the realm of material transport, moving tens of millions of tons of diverse cargo across vast areas every year. As effective as they are at doing this, conventional conveyors have one distinct disadvantage — they can only move the material in one direction. Many applications require the material to be moved in several directions on the conveyor bed, however, necessitating a unique solution. The ball transfer unit is one such solution that allows goods placed on the conveyor bed to be moved in all directions.

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Man with a drill

The ball transfer unit is a relatively simple, non-powered device that relies on the smooth, friction-free motion inherent in freely-rotating ball bearings. These devices consist of a large ball bearing enclosed in a tubular casing that is crimped or restricted on one of its ends. This restriction holds the ball bearing captive in the casing while allowing it to rotate freely, with a portion of its surface protruding from the tube. Arranged in a hemispherical cup below the large ball are a layer of smaller balls in constant contact with the lower surface of the large ball. This allows the large ball to rotate smoothly in all directions with a minimum of friction.

A number of these ball transfer units are then mounted on a flat plate or runner. These plates are then arranged in rows against one another on the conveyor bed. This arrangement presents a large surface of free-rotating balls upon which material can be moved around smoothly in all directions. Another benefit of the modular nature of these conveyors is the easy replacement of any individual ball transfer unit that suffers damage or otherwise becomes non-operational. The low profile and modest size of these units also make them ideal for applications where similar devices, such as the Mecanum wheel and omni wheel, are not suitable.

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