Using the principles of tribology, the Ball Transfer Unit offers an efficient method of moving loads, materials and equipment accurately and with instant directional change.

It is not widely known that the Ball Transfer Unit started life as a humble furniture castor. In the 1940 and 1950s Alwayse Engineering was producing ball units as an alternative to a castor for chairs, cabinets and other pieces of furniture. Then, it was approached by a company looking to move cargo pallets in aircraft and the Ball Transfer Unit was born.

 

Alwayse Engineering designed a flanged unit which was mounted in the floor of the cargo hold in an evenly spaced array. Units were orientated with the load ball facing up which allowed the cargo pallets to move easily over the deck and be positioned accurately with a minimum of effort. Thus the first air cargo decks were developed.

As in the case of the original air cargo decks, an array of ball transfer units set into either channels or fabricated table tops provides an efficient method of moving loads, materials and equipment.

Ball tables have been providing solutions acrossOnt a wide range of industries such as automotive assembly and testing, materials handling, medical imaging equipment, and food and beverage packaging systems. With load capacities of up to 4000kg on one unit, ball tables are a proven solution when heavy tooling, dies or machinery needs to be accurately positioned.

In its simplest form the ball transfer unit is comprised of a housing formed from pressed or machined steel, or in some cases injection moulded Glass Reinforced Nylon, featuring an integral hemispherical cup. The load ball sits on top of many minor balls set in the base of the cup. The unit is then encapsulated with an outer ring to retain the load and minor balls.

As the load ball surface contact is spread over so many minor balls, it benefits from both low friction and high load capacity. The friction coefficient for a Ball Transfer Unit is typically between 1 and 2% of the load being passed over the unit, meaning that a load of 1000kg may require only 100N of force per unit. Loads are usually supported on a minimum of 4 units; therefore the force required will drop to 25N.

 

Whilst the principle of the ball transfer unit has remained relatively unchanged, there have been a number of key developments in materials and the internal workings, often as a result of developing a bespoke solution to a specific application.

 

Steel and nylon, can be replaced with specialist materials to meet extreme and unique conditions. For instance, Phenolic resin balls can be used to provide increased working temperatures; silicon nitride for low magnetic permeability and the thermoplastic polymer PEEK which allows movement of particularly delicate materials.

 

This is demonstrated in the use of Ball Transfer Units in the down pipe applications of the Oil and Gas extraction industry where the use of ruby and silicon nitride is commonplace due to their hardwearing properties.

 

Within the handling and storing industry ball tables are commonly combined with roller conveyors to enable materials and pallets to be readily rotated, simply and efficiently by hand. In production engineering they are the simplest way to move heavy pieces of equipment such as machine tools, and with the use of a ‘live-dead’ table, the ability to manoeuvre equipment precisely then effectively lock it in place.

 

The principle of a ‘live-dead’ table involves using ball units set in an array on a plate or table which can move the units up or down by hydraulic, pneumatic or mechanical means. When the ball units are raised the load balls are exposed through the table top – this is the ‘live’ position and the equipment or materials can move freely. In the ‘dead’ position, the ball units are lowered effectively locking the items in place.

 

Such solutions can used for many different applications.